1// -*- C++ -*-
2//===-------------------------- algorithm ---------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP_ALGORITHM
11#define _LIBCPP_ALGORITHM
12
13/*
14    algorithm synopsis
15
16#include <initializer_list>
17
18namespace std
19{
20
21template <class InputIterator, class Predicate>
22    constexpr bool     // constexpr in C++20
23    all_of(InputIterator first, InputIterator last, Predicate pred);
24
25template <class InputIterator, class Predicate>
26    constexpr bool     // constexpr in C++20
27    any_of(InputIterator first, InputIterator last, Predicate pred);
28
29template <class InputIterator, class Predicate>
30    constexpr bool     // constexpr in C++20
31    none_of(InputIterator first, InputIterator last, Predicate pred);
32
33template <class InputIterator, class Function>
34    constexpr Function          // constexpr in C++20
35    for_each(InputIterator first, InputIterator last, Function f);
36
37template<class InputIterator, class Size, class Function>
38    constexpr InputIterator     // constexpr in C++20
39    for_each_n(InputIterator first, Size n, Function f); // C++17
40
41template <class InputIterator, class T>
42    constexpr InputIterator     // constexpr in C++20
43    find(InputIterator first, InputIterator last, const T& value);
44
45template <class InputIterator, class Predicate>
46    constexpr InputIterator     // constexpr in C++20
47    find_if(InputIterator first, InputIterator last, Predicate pred);
48
49template<class InputIterator, class Predicate>
50    InputIterator               // constexpr in C++20
51    find_if_not(InputIterator first, InputIterator last, Predicate pred);
52
53template <class ForwardIterator1, class ForwardIterator2>
54    ForwardIterator1            // constexpr in C++20
55    find_end(ForwardIterator1 first1, ForwardIterator1 last1,
56             ForwardIterator2 first2, ForwardIterator2 last2);
57
58template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
59    ForwardIterator1            // constexpr in C++20
60    find_end(ForwardIterator1 first1, ForwardIterator1 last1,
61             ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred);
62
63template <class ForwardIterator1, class ForwardIterator2>
64    constexpr ForwardIterator1  // constexpr in C++20
65    find_first_of(ForwardIterator1 first1, ForwardIterator1 last1,
66                  ForwardIterator2 first2, ForwardIterator2 last2);
67
68template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
69    constexpr ForwardIterator1  // constexpr in C++20
70    find_first_of(ForwardIterator1 first1, ForwardIterator1 last1,
71                  ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred);
72
73template <class ForwardIterator>
74    constexpr ForwardIterator   // constexpr in C++20
75    adjacent_find(ForwardIterator first, ForwardIterator last);
76
77template <class ForwardIterator, class BinaryPredicate>
78    constexpr ForwardIterator   // constexpr in C++20
79    adjacent_find(ForwardIterator first, ForwardIterator last, BinaryPredicate pred);
80
81template <class InputIterator, class T>
82    constexpr typename iterator_traits<InputIterator>::difference_type  // constexpr in C++20
83    count(InputIterator first, InputIterator last, const T& value);
84
85template <class InputIterator, class Predicate>
86    constexpr typename iterator_traits<InputIterator>::difference_type // constexpr in C++20
87    count_if(InputIterator first, InputIterator last, Predicate pred);
88
89template <class InputIterator1, class InputIterator2>
90    constexpr pair<InputIterator1, InputIterator2>   // constexpr in C++20
91    mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2);
92
93template <class InputIterator1, class InputIterator2>
94    constexpr pair<InputIterator1, InputIterator2>   // constexpr in C++20
95    mismatch(InputIterator1 first1, InputIterator1 last1,
96             InputIterator2 first2, InputIterator2 last2); // **C++14**
97
98template <class InputIterator1, class InputIterator2, class BinaryPredicate>
99    constexpr pair<InputIterator1, InputIterator2>   // constexpr in C++20
100    mismatch(InputIterator1 first1, InputIterator1 last1,
101             InputIterator2 first2, BinaryPredicate pred);
102
103template <class InputIterator1, class InputIterator2, class BinaryPredicate>
104    constexpr pair<InputIterator1, InputIterator2>   // constexpr in C++20
105    mismatch(InputIterator1 first1, InputIterator1 last1,
106             InputIterator2 first2, InputIterator2 last2,
107             BinaryPredicate pred); // **C++14**
108
109template <class InputIterator1, class InputIterator2>
110    constexpr bool      // constexpr in C++20
111    equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2);
112
113template <class InputIterator1, class InputIterator2>
114    constexpr bool      // constexpr in C++20
115    equal(InputIterator1 first1, InputIterator1 last1,
116          InputIterator2 first2, InputIterator2 last2); // **C++14**
117
118template <class InputIterator1, class InputIterator2, class BinaryPredicate>
119    constexpr bool      // constexpr in C++20
120    equal(InputIterator1 first1, InputIterator1 last1,
121          InputIterator2 first2, BinaryPredicate pred);
122
123template <class InputIterator1, class InputIterator2, class BinaryPredicate>
124    constexpr bool      // constexpr in C++20
125    equal(InputIterator1 first1, InputIterator1 last1,
126          InputIterator2 first2, InputIterator2 last2,
127          BinaryPredicate pred); // **C++14**
128
129template<class ForwardIterator1, class ForwardIterator2>
130    constexpr bool      // constexpr in C++20
131    is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
132                   ForwardIterator2 first2);
133
134template<class ForwardIterator1, class ForwardIterator2>
135    constexpr bool      // constexpr in C++20
136    is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
137                   ForwardIterator2 first2, ForwardIterator2 last2); // **C++14**
138
139template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
140    constexpr bool      // constexpr in C++20
141    is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
142                   ForwardIterator2 first2, BinaryPredicate pred);
143
144template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
145    constexpr bool      // constexpr in C++20
146    is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
147                   ForwardIterator2 first2, ForwardIterator2 last2,
148                   BinaryPredicate pred);  // **C++14**
149
150template <class ForwardIterator1, class ForwardIterator2>
151    constexpr ForwardIterator1      // constexpr in C++20
152    search(ForwardIterator1 first1, ForwardIterator1 last1,
153           ForwardIterator2 first2, ForwardIterator2 last2);
154
155template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
156    constexpr ForwardIterator1      // constexpr in C++20
157    search(ForwardIterator1 first1, ForwardIterator1 last1,
158           ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred);
159
160template <class ForwardIterator, class Size, class T>
161    constexpr ForwardIterator       // constexpr in C++20
162    search_n(ForwardIterator first, ForwardIterator last, Size count, const T& value);
163
164template <class ForwardIterator, class Size, class T, class BinaryPredicate>
165    constexpr ForwardIterator       // constexpr in C++20
166    search_n(ForwardIterator first, ForwardIterator last,
167             Size count, const T& value, BinaryPredicate pred);
168
169template <class InputIterator, class OutputIterator>
170    OutputIterator
171    copy(InputIterator first, InputIterator last, OutputIterator result);
172
173template<class InputIterator, class OutputIterator, class Predicate>
174    OutputIterator
175    copy_if(InputIterator first, InputIterator last,
176            OutputIterator result, Predicate pred);
177
178template<class InputIterator, class Size, class OutputIterator>
179    OutputIterator
180    copy_n(InputIterator first, Size n, OutputIterator result);
181
182template <class BidirectionalIterator1, class BidirectionalIterator2>
183    BidirectionalIterator2
184    copy_backward(BidirectionalIterator1 first, BidirectionalIterator1 last,
185                  BidirectionalIterator2 result);
186
187template <class ForwardIterator1, class ForwardIterator2>
188    ForwardIterator2
189    swap_ranges(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2);
190
191template <class ForwardIterator1, class ForwardIterator2>
192    void
193    iter_swap(ForwardIterator1 a, ForwardIterator2 b);
194
195template <class InputIterator, class OutputIterator, class UnaryOperation>
196    constexpr OutputIterator      // constexpr in C++20
197    transform(InputIterator first, InputIterator last, OutputIterator result, UnaryOperation op);
198
199template <class InputIterator1, class InputIterator2, class OutputIterator, class BinaryOperation>
200    constexpr OutputIterator      // constexpr in C++20
201    transform(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2,
202              OutputIterator result, BinaryOperation binary_op);
203
204template <class ForwardIterator, class T>
205    constexpr void      // constexpr in C++20
206    replace(ForwardIterator first, ForwardIterator last, const T& old_value, const T& new_value);
207
208template <class ForwardIterator, class Predicate, class T>
209    constexpr void      // constexpr in C++20
210    replace_if(ForwardIterator first, ForwardIterator last, Predicate pred, const T& new_value);
211
212template <class InputIterator, class OutputIterator, class T>
213    constexpr OutputIterator      // constexpr in C++20
214    replace_copy(InputIterator first, InputIterator last, OutputIterator result,
215                 const T& old_value, const T& new_value);
216
217template <class InputIterator, class OutputIterator, class Predicate, class T>
218    constexpr OutputIterator      // constexpr in C++20
219    replace_copy_if(InputIterator first, InputIterator last, OutputIterator result, Predicate pred, const T& new_value);
220
221template <class ForwardIterator, class T>
222    constexpr void      // constexpr in C++20
223    fill(ForwardIterator first, ForwardIterator last, const T& value);
224
225template <class OutputIterator, class Size, class T>
226    constexpr OutputIterator      // constexpr in C++20
227    fill_n(OutputIterator first, Size n, const T& value);
228
229template <class ForwardIterator, class Generator>
230    constexpr void      // constexpr in C++20
231    generate(ForwardIterator first, ForwardIterator last, Generator gen);
232
233template <class OutputIterator, class Size, class Generator>
234    constexpr OutputIterator      // constexpr in C++20
235    generate_n(OutputIterator first, Size n, Generator gen);
236
237template <class ForwardIterator, class T>
238    constexpr ForwardIterator     // constexpr in C++20
239    remove(ForwardIterator first, ForwardIterator last, const T& value);
240
241template <class ForwardIterator, class Predicate>
242    constexpr ForwardIterator     // constexpr in C++20
243    remove_if(ForwardIterator first, ForwardIterator last, Predicate pred);
244
245template <class InputIterator, class OutputIterator, class T>
246    constexpr OutputIterator     // constexpr in C++20
247    remove_copy(InputIterator first, InputIterator last, OutputIterator result, const T& value);
248
249template <class InputIterator, class OutputIterator, class Predicate>
250    constexpr OutputIterator     // constexpr in C++20
251    remove_copy_if(InputIterator first, InputIterator last, OutputIterator result, Predicate pred);
252
253template <class ForwardIterator>
254    ForwardIterator
255    unique(ForwardIterator first, ForwardIterator last);
256
257template <class ForwardIterator, class BinaryPredicate>
258    ForwardIterator
259    unique(ForwardIterator first, ForwardIterator last, BinaryPredicate pred);
260
261template <class InputIterator, class OutputIterator>
262    OutputIterator
263    unique_copy(InputIterator first, InputIterator last, OutputIterator result);
264
265template <class InputIterator, class OutputIterator, class BinaryPredicate>
266    OutputIterator
267    unique_copy(InputIterator first, InputIterator last, OutputIterator result, BinaryPredicate pred);
268
269template <class BidirectionalIterator>
270    void
271    reverse(BidirectionalIterator first, BidirectionalIterator last);
272
273template <class BidirectionalIterator, class OutputIterator>
274    constexpr OutputIterator       // constexpr in C++20
275    reverse_copy(BidirectionalIterator first, BidirectionalIterator last, OutputIterator result);
276
277template <class ForwardIterator>
278    ForwardIterator
279    rotate(ForwardIterator first, ForwardIterator middle, ForwardIterator last);
280
281template <class ForwardIterator, class OutputIterator>
282    OutputIterator
283    rotate_copy(ForwardIterator first, ForwardIterator middle, ForwardIterator last, OutputIterator result);
284
285template <class RandomAccessIterator>
286    void
287    random_shuffle(RandomAccessIterator first, RandomAccessIterator last); // deprecated in C++14, removed in C++17
288
289template <class RandomAccessIterator, class RandomNumberGenerator>
290    void
291    random_shuffle(RandomAccessIterator first, RandomAccessIterator last,
292                   RandomNumberGenerator& rand);  // deprecated in C++14, removed in C++17
293
294template<class PopulationIterator, class SampleIterator,
295         class Distance, class UniformRandomBitGenerator>
296    SampleIterator sample(PopulationIterator first, PopulationIterator last,
297                          SampleIterator out, Distance n,
298                          UniformRandomBitGenerator&& g); // C++17
299
300template<class RandomAccessIterator, class UniformRandomNumberGenerator>
301    void shuffle(RandomAccessIterator first, RandomAccessIterator last,
302                 UniformRandomNumberGenerator&& g);
303
304template <class InputIterator, class Predicate>
305    constexpr bool  // constexpr in C++20
306    is_partitioned(InputIterator first, InputIterator last, Predicate pred);
307
308template <class ForwardIterator, class Predicate>
309    ForwardIterator
310    partition(ForwardIterator first, ForwardIterator last, Predicate pred);
311
312template <class InputIterator, class OutputIterator1,
313          class OutputIterator2, class Predicate>
314    constexpr pair<OutputIterator1, OutputIterator2>   // constexpr in C++20
315    partition_copy(InputIterator first, InputIterator last,
316                   OutputIterator1 out_true, OutputIterator2 out_false,
317                   Predicate pred);
318
319template <class ForwardIterator, class Predicate>
320    ForwardIterator
321    stable_partition(ForwardIterator first, ForwardIterator last, Predicate pred);
322
323template<class ForwardIterator, class Predicate>
324    constexpr ForwardIterator  // constexpr in C++20
325    partition_point(ForwardIterator first, ForwardIterator last, Predicate pred);
326
327template <class ForwardIterator>
328    constexpr bool  // constexpr in C++20
329    is_sorted(ForwardIterator first, ForwardIterator last);
330
331template <class ForwardIterator, class Compare>
332    bool
333    is_sorted(ForwardIterator first, ForwardIterator last, Compare comp);
334
335template<class ForwardIterator>
336    constexpr ForwardIterator    // constexpr in C++20
337    is_sorted_until(ForwardIterator first, ForwardIterator last);
338
339template <class ForwardIterator, class Compare>
340    constexpr ForwardIterator    // constexpr in C++20
341    is_sorted_until(ForwardIterator first, ForwardIterator last, Compare comp);
342
343template <class RandomAccessIterator>
344    void
345    sort(RandomAccessIterator first, RandomAccessIterator last);
346
347template <class RandomAccessIterator, class Compare>
348    void
349    sort(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
350
351template <class RandomAccessIterator>
352    void
353    stable_sort(RandomAccessIterator first, RandomAccessIterator last);
354
355template <class RandomAccessIterator, class Compare>
356    void
357    stable_sort(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
358
359template <class RandomAccessIterator>
360    void
361    partial_sort(RandomAccessIterator first, RandomAccessIterator middle, RandomAccessIterator last);
362
363template <class RandomAccessIterator, class Compare>
364    void
365    partial_sort(RandomAccessIterator first, RandomAccessIterator middle, RandomAccessIterator last, Compare comp);
366
367template <class InputIterator, class RandomAccessIterator>
368    RandomAccessIterator
369    partial_sort_copy(InputIterator first, InputIterator last,
370                      RandomAccessIterator result_first, RandomAccessIterator result_last);
371
372template <class InputIterator, class RandomAccessIterator, class Compare>
373    RandomAccessIterator
374    partial_sort_copy(InputIterator first, InputIterator last,
375                      RandomAccessIterator result_first, RandomAccessIterator result_last, Compare comp);
376
377template <class RandomAccessIterator>
378    void
379    nth_element(RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last);
380
381template <class RandomAccessIterator, class Compare>
382    void
383    nth_element(RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last, Compare comp);
384
385template <class ForwardIterator, class T>
386    constexpr ForwardIterator                         // constexpr in C++20
387    lower_bound(ForwardIterator first, ForwardIterator last, const T& value);
388
389template <class ForwardIterator, class T, class Compare>
390    constexpr ForwardIterator                         // constexpr in C++20
391    lower_bound(ForwardIterator first, ForwardIterator last, const T& value, Compare comp);
392
393template <class ForwardIterator, class T>
394    constexpr ForwardIterator                         // constexpr in C++20
395    upper_bound(ForwardIterator first, ForwardIterator last, const T& value);
396
397template <class ForwardIterator, class T, class Compare>
398    constexpr ForwardIterator                         // constexpr in C++20
399    upper_bound(ForwardIterator first, ForwardIterator last, const T& value, Compare comp);
400
401template <class ForwardIterator, class T>
402    constexpr pair<ForwardIterator, ForwardIterator>  // constexpr in C++20
403    equal_range(ForwardIterator first, ForwardIterator last, const T& value);
404
405template <class ForwardIterator, class T, class Compare>
406    constexpr pair<ForwardIterator, ForwardIterator>  // constexpr in C++20
407    equal_range(ForwardIterator first, ForwardIterator last, const T& value, Compare comp);
408
409template <class ForwardIterator, class T>
410    constexpr bool                                    // constexpr in C++20
411    binary_search(ForwardIterator first, ForwardIterator last, const T& value);
412
413template <class ForwardIterator, class T, class Compare>
414    constexpr bool                                    // constexpr in C++20
415    binary_search(ForwardIterator first, ForwardIterator last, const T& value, Compare comp);
416
417template <class InputIterator1, class InputIterator2, class OutputIterator>
418    OutputIterator
419    merge(InputIterator1 first1, InputIterator1 last1,
420          InputIterator2 first2, InputIterator2 last2, OutputIterator result);
421
422template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
423    OutputIterator
424    merge(InputIterator1 first1, InputIterator1 last1,
425          InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
426
427template <class BidirectionalIterator>
428    void
429    inplace_merge(BidirectionalIterator first, BidirectionalIterator middle, BidirectionalIterator last);
430
431template <class BidirectionalIterator, class Compare>
432    void
433    inplace_merge(BidirectionalIterator first, BidirectionalIterator middle, BidirectionalIterator last, Compare comp);
434
435template <class InputIterator1, class InputIterator2>
436    constexpr bool                                    // constexpr in C++20
437    includes(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2);
438
439template <class InputIterator1, class InputIterator2, class Compare>
440    constexpr bool                                    // constexpr in C++20
441    includes(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp);
442
443template <class InputIterator1, class InputIterator2, class OutputIterator>
444    OutputIterator
445    set_union(InputIterator1 first1, InputIterator1 last1,
446              InputIterator2 first2, InputIterator2 last2, OutputIterator result);
447
448template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
449    OutputIterator
450    set_union(InputIterator1 first1, InputIterator1 last1,
451              InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
452
453template <class InputIterator1, class InputIterator2, class OutputIterator>
454    constexpr OutputIterator                         // constexpr in C++20
455    set_intersection(InputIterator1 first1, InputIterator1 last1,
456                     InputIterator2 first2, InputIterator2 last2, OutputIterator result);
457
458template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
459    constexpr OutputIterator                         // constexpr in C++20
460    set_intersection(InputIterator1 first1, InputIterator1 last1,
461                     InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
462
463template <class InputIterator1, class InputIterator2, class OutputIterator>
464    OutputIterator
465    set_difference(InputIterator1 first1, InputIterator1 last1,
466                   InputIterator2 first2, InputIterator2 last2, OutputIterator result);
467
468template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
469    OutputIterator
470    set_difference(InputIterator1 first1, InputIterator1 last1,
471                   InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
472
473template <class InputIterator1, class InputIterator2, class OutputIterator>
474    OutputIterator
475    set_symmetric_difference(InputIterator1 first1, InputIterator1 last1,
476                             InputIterator2 first2, InputIterator2 last2, OutputIterator result);
477
478template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
479    OutputIterator
480    set_symmetric_difference(InputIterator1 first1, InputIterator1 last1,
481                             InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
482
483template <class RandomAccessIterator>
484    void
485    push_heap(RandomAccessIterator first, RandomAccessIterator last);
486
487template <class RandomAccessIterator, class Compare>
488    void
489    push_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
490
491template <class RandomAccessIterator>
492    void
493    pop_heap(RandomAccessIterator first, RandomAccessIterator last);
494
495template <class RandomAccessIterator, class Compare>
496    void
497    pop_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
498
499template <class RandomAccessIterator>
500    void
501    make_heap(RandomAccessIterator first, RandomAccessIterator last);
502
503template <class RandomAccessIterator, class Compare>
504    void
505    make_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
506
507template <class RandomAccessIterator>
508    void
509    sort_heap(RandomAccessIterator first, RandomAccessIterator last);
510
511template <class RandomAccessIterator, class Compare>
512    void
513    sort_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
514
515template <class RandomAccessIterator>
516    constexpr bool   // constexpr in C++20
517    is_heap(RandomAccessIterator first, RandomAccessiterator last);
518
519template <class RandomAccessIterator, class Compare>
520    constexpr bool   // constexpr in C++20
521    is_heap(RandomAccessIterator first, RandomAccessiterator last, Compare comp);
522
523template <class RandomAccessIterator>
524    constexpr RandomAccessIterator   // constexpr in C++20
525    is_heap_until(RandomAccessIterator first, RandomAccessiterator last);
526
527template <class RandomAccessIterator, class Compare>
528    constexpr RandomAccessIterator   // constexpr in C++20
529    is_heap_until(RandomAccessIterator first, RandomAccessiterator last, Compare comp);
530
531template <class ForwardIterator>
532    ForwardIterator
533    min_element(ForwardIterator first, ForwardIterator last);  // constexpr in C++14
534
535template <class ForwardIterator, class Compare>
536    ForwardIterator
537    min_element(ForwardIterator first, ForwardIterator last, Compare comp);  // constexpr in C++14
538
539template <class T>
540    const T&
541    min(const T& a, const T& b);  // constexpr in C++14
542
543template <class T, class Compare>
544    const T&
545    min(const T& a, const T& b, Compare comp);  // constexpr in C++14
546
547template<class T>
548    T
549    min(initializer_list<T> t);  // constexpr in C++14
550
551template<class T, class Compare>
552    T
553    min(initializer_list<T> t, Compare comp);  // constexpr in C++14
554
555template<class T>
556    constexpr const T& clamp( const T& v, const T& lo, const T& hi );               // C++17
557
558template<class T, class Compare>
559    constexpr const T& clamp( const T& v, const T& lo, const T& hi, Compare comp ); // C++17
560
561template <class ForwardIterator>
562    ForwardIterator
563    max_element(ForwardIterator first, ForwardIterator last);  // constexpr in C++14
564
565template <class ForwardIterator, class Compare>
566    ForwardIterator
567    max_element(ForwardIterator first, ForwardIterator last, Compare comp);  // constexpr in C++14
568
569template <class T>
570    const T&
571    max(const T& a, const T& b); // constexpr in C++14
572
573template <class T, class Compare>
574    const T&
575    max(const T& a, const T& b, Compare comp);  // constexpr in C++14
576
577template<class T>
578    T
579    max(initializer_list<T> t);  // constexpr in C++14
580
581template<class T, class Compare>
582    T
583    max(initializer_list<T> t, Compare comp);  // constexpr in C++14
584
585template<class ForwardIterator>
586    pair<ForwardIterator, ForwardIterator>
587    minmax_element(ForwardIterator first, ForwardIterator last);   // constexpr in C++14
588
589template<class ForwardIterator, class Compare>
590    pair<ForwardIterator, ForwardIterator>
591    minmax_element(ForwardIterator first, ForwardIterator last, Compare comp);   // constexpr in C++14
592
593template<class T>
594    pair<const T&, const T&>
595    minmax(const T& a, const T& b);  // constexpr in C++14
596
597template<class T, class Compare>
598    pair<const T&, const T&>
599    minmax(const T& a, const T& b, Compare comp);  // constexpr in C++14
600
601template<class T>
602    pair<T, T>
603    minmax(initializer_list<T> t);  // constexpr in C++14
604
605template<class T, class Compare>
606    pair<T, T>
607    minmax(initializer_list<T> t, Compare comp);  // constexpr in C++14
608
609template <class InputIterator1, class InputIterator2>
610    constexpr bool     // constexpr in C++20
611    lexicographical_compare(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2);
612
613template <class InputIterator1, class InputIterator2, class Compare>
614    constexpr bool     // constexpr in C++20
615    lexicographical_compare(InputIterator1 first1, InputIterator1 last1,
616                            InputIterator2 first2, InputIterator2 last2, Compare comp);
617
618template <class BidirectionalIterator>
619    bool
620    next_permutation(BidirectionalIterator first, BidirectionalIterator last);
621
622template <class BidirectionalIterator, class Compare>
623    bool
624    next_permutation(BidirectionalIterator first, BidirectionalIterator last, Compare comp);
625
626template <class BidirectionalIterator>
627    bool
628    prev_permutation(BidirectionalIterator first, BidirectionalIterator last);
629
630template <class BidirectionalIterator, class Compare>
631    bool
632    prev_permutation(BidirectionalIterator first, BidirectionalIterator last, Compare comp);
633
634}  // std
635
636*/
637
638#include <__config>
639#include <initializer_list>
640#include <type_traits>
641#include <cstring>
642#include <utility> // needed to provide swap_ranges.
643#include <memory>
644#include <functional>
645#include <iterator>
646#include <cstddef>
647#include <bit>
648#include <version>
649
650#include <__debug>
651
652#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
653#pragma GCC system_header
654#endif
655
656_LIBCPP_PUSH_MACROS
657#include <__undef_macros>
658
659
660_LIBCPP_BEGIN_NAMESPACE_STD
661
662// I'd like to replace these with _VSTD::equal_to<void>, but can't because:
663//   * That only works with C++14 and later, and
664//   * We haven't included <functional> here.
665template <class _T1, class _T2 = _T1>
666struct __equal_to
667{
668    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 bool operator()(const _T1& __x, const _T1& __y) const {return __x == __y;}
669    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 bool operator()(const _T1& __x, const _T2& __y) const {return __x == __y;}
670    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 bool operator()(const _T2& __x, const _T1& __y) const {return __x == __y;}
671    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 bool operator()(const _T2& __x, const _T2& __y) const {return __x == __y;}
672};
673
674template <class _T1>
675struct __equal_to<_T1, _T1>
676{
677    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
678    bool operator()(const _T1& __x, const _T1& __y) const {return __x == __y;}
679};
680
681template <class _T1>
682struct __equal_to<const _T1, _T1>
683{
684    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
685    bool operator()(const _T1& __x, const _T1& __y) const {return __x == __y;}
686};
687
688template <class _T1>
689struct __equal_to<_T1, const _T1>
690{
691    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
692    bool operator()(const _T1& __x, const _T1& __y) const {return __x == __y;}
693};
694
695template <class _T1, class _T2 = _T1>
696struct __less
697{
698    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
699    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
700
701    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
702    bool operator()(const _T1& __x, const _T2& __y) const {return __x < __y;}
703
704    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
705    bool operator()(const _T2& __x, const _T1& __y) const {return __x < __y;}
706
707    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
708    bool operator()(const _T2& __x, const _T2& __y) const {return __x < __y;}
709};
710
711template <class _T1>
712struct __less<_T1, _T1>
713{
714    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
715    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
716};
717
718template <class _T1>
719struct __less<const _T1, _T1>
720{
721    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
722    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
723};
724
725template <class _T1>
726struct __less<_T1, const _T1>
727{
728    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
729    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
730};
731
732template <class _Predicate>
733class __invert // invert the sense of a comparison
734{
735private:
736    _Predicate __p_;
737public:
738    _LIBCPP_INLINE_VISIBILITY __invert() {}
739
740    _LIBCPP_INLINE_VISIBILITY
741    explicit __invert(_Predicate __p) : __p_(__p) {}
742
743    template <class _T1>
744    _LIBCPP_INLINE_VISIBILITY
745    bool operator()(const _T1& __x) {return !__p_(__x);}
746
747    template <class _T1, class _T2>
748    _LIBCPP_INLINE_VISIBILITY
749    bool operator()(const _T1& __x, const _T2& __y) {return __p_(__y, __x);}
750};
751
752// Perform division by two quickly for positive integers (llvm.org/PR39129)
753
754template <typename _Integral>
755_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
756typename enable_if
757<
758    is_integral<_Integral>::value,
759    _Integral
760>::type
761__half_positive(_Integral __value)
762{
763    return static_cast<_Integral>(static_cast<typename make_unsigned<_Integral>::type>(__value) / 2);
764}
765
766template <typename _Tp>
767_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
768typename enable_if
769<
770    !is_integral<_Tp>::value,
771    _Tp
772>::type
773__half_positive(_Tp __value)
774{
775    return __value / 2;
776}
777
778#ifdef _LIBCPP_DEBUG
779
780template <class _Compare>
781struct __debug_less
782{
783    _Compare __comp_;
784    __debug_less(_Compare& __c) : __comp_(__c) {}
785
786    template <class _Tp, class _Up>
787    bool operator()(_Tp& __x,  _Up& __y)
788    {
789        bool __r = __comp_(__x, __y);
790        if (__r)
791            __do_compare_assert(0, __y, __x);
792        return __r;
793    }
794
795    template <class _LHS, class _RHS>
796    inline _LIBCPP_INLINE_VISIBILITY
797    decltype((void)_VSTD::declval<_Compare&>()(
798        _VSTD::declval<_LHS &>(), _VSTD::declval<_RHS &>()))
799    __do_compare_assert(int, _LHS & __l, _RHS & __r) {
800        _LIBCPP_ASSERT(!__comp_(__l, __r),
801            "Comparator does not induce a strict weak ordering");
802    }
803
804    template <class _LHS, class _RHS>
805    inline _LIBCPP_INLINE_VISIBILITY
806    void __do_compare_assert(long, _LHS &, _RHS &) {}
807};
808
809#endif // _LIBCPP_DEBUG
810
811// all_of
812
813template <class _InputIterator, class _Predicate>
814_LIBCPP_NODISCARD_EXT inline
815_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
816bool
817all_of(_InputIterator __first, _InputIterator __last, _Predicate __pred)
818{
819    for (; __first != __last; ++__first)
820        if (!__pred(*__first))
821            return false;
822    return true;
823}
824
825// any_of
826
827template <class _InputIterator, class _Predicate>
828_LIBCPP_NODISCARD_EXT inline
829_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
830bool
831any_of(_InputIterator __first, _InputIterator __last, _Predicate __pred)
832{
833    for (; __first != __last; ++__first)
834        if (__pred(*__first))
835            return true;
836    return false;
837}
838
839// none_of
840
841template <class _InputIterator, class _Predicate>
842_LIBCPP_NODISCARD_EXT inline
843_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
844bool
845none_of(_InputIterator __first, _InputIterator __last, _Predicate __pred)
846{
847    for (; __first != __last; ++__first)
848        if (__pred(*__first))
849            return false;
850    return true;
851}
852
853// for_each
854
855template <class _InputIterator, class _Function>
856inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
857_Function
858for_each(_InputIterator __first, _InputIterator __last, _Function __f)
859{
860    for (; __first != __last; ++__first)
861        __f(*__first);
862    return __f;
863}
864
865#if _LIBCPP_STD_VER > 14
866// for_each_n
867
868template <class _InputIterator, class _Size, class _Function>
869inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
870_InputIterator
871for_each_n(_InputIterator __first, _Size __orig_n, _Function __f)
872{
873    typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;
874    _IntegralSize __n = __orig_n;
875    while (__n > 0)
876    {
877         __f(*__first);
878         ++__first;
879         --__n;
880    }
881    return __first;
882}
883#endif
884
885// find
886
887template <class _InputIterator, class _Tp>
888_LIBCPP_NODISCARD_EXT inline
889_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
890_InputIterator
891find(_InputIterator __first, _InputIterator __last, const _Tp& __value_)
892{
893    for (; __first != __last; ++__first)
894        if (*__first == __value_)
895            break;
896    return __first;
897}
898
899// find_if
900
901template <class _InputIterator, class _Predicate>
902_LIBCPP_NODISCARD_EXT inline
903_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
904_InputIterator
905find_if(_InputIterator __first, _InputIterator __last, _Predicate __pred)
906{
907    for (; __first != __last; ++__first)
908        if (__pred(*__first))
909            break;
910    return __first;
911}
912
913// find_if_not
914
915template<class _InputIterator, class _Predicate>
916_LIBCPP_NODISCARD_EXT inline
917_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
918_InputIterator
919find_if_not(_InputIterator __first, _InputIterator __last, _Predicate __pred)
920{
921    for (; __first != __last; ++__first)
922        if (!__pred(*__first))
923            break;
924    return __first;
925}
926
927// find_end
928
929template <class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
930_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator1
931__find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
932           _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred,
933           forward_iterator_tag, forward_iterator_tag)
934{
935    // modeled after search algorithm
936    _ForwardIterator1 __r = __last1;  // __last1 is the "default" answer
937    if (__first2 == __last2)
938        return __r;
939    while (true)
940    {
941        while (true)
942        {
943            if (__first1 == __last1)         // if source exhausted return last correct answer
944                return __r;                  //    (or __last1 if never found)
945            if (__pred(*__first1, *__first2))
946                break;
947            ++__first1;
948        }
949        // *__first1 matches *__first2, now match elements after here
950        _ForwardIterator1 __m1 = __first1;
951        _ForwardIterator2 __m2 = __first2;
952        while (true)
953        {
954            if (++__m2 == __last2)
955            {                         // Pattern exhaused, record answer and search for another one
956                __r = __first1;
957                ++__first1;
958                break;
959            }
960            if (++__m1 == __last1)     // Source exhausted, return last answer
961                return __r;
962            if (!__pred(*__m1, *__m2))  // mismatch, restart with a new __first
963            {
964                ++__first1;
965                break;
966            }  // else there is a match, check next elements
967        }
968    }
969}
970
971template <class _BinaryPredicate, class _BidirectionalIterator1, class _BidirectionalIterator2>
972_LIBCPP_CONSTEXPR_AFTER_CXX17 _BidirectionalIterator1
973__find_end(_BidirectionalIterator1 __first1, _BidirectionalIterator1 __last1,
974           _BidirectionalIterator2 __first2, _BidirectionalIterator2 __last2, _BinaryPredicate __pred,
975           bidirectional_iterator_tag, bidirectional_iterator_tag)
976{
977    // modeled after search algorithm (in reverse)
978    if (__first2 == __last2)
979        return __last1;  // Everything matches an empty sequence
980    _BidirectionalIterator1 __l1 = __last1;
981    _BidirectionalIterator2 __l2 = __last2;
982    --__l2;
983    while (true)
984    {
985        // Find last element in sequence 1 that matchs *(__last2-1), with a mininum of loop checks
986        while (true)
987        {
988            if (__first1 == __l1)  // return __last1 if no element matches *__first2
989                return __last1;
990            if (__pred(*--__l1, *__l2))
991                break;
992        }
993        // *__l1 matches *__l2, now match elements before here
994        _BidirectionalIterator1 __m1 = __l1;
995        _BidirectionalIterator2 __m2 = __l2;
996        while (true)
997        {
998            if (__m2 == __first2)  // If pattern exhausted, __m1 is the answer (works for 1 element pattern)
999                return __m1;
1000            if (__m1 == __first1)  // Otherwise if source exhaused, pattern not found
1001                return __last1;
1002            if (!__pred(*--__m1, *--__m2))  // if there is a mismatch, restart with a new __l1
1003            {
1004                break;
1005            }  // else there is a match, check next elements
1006        }
1007    }
1008}
1009
1010template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
1011_LIBCPP_CONSTEXPR_AFTER_CXX11 _RandomAccessIterator1
1012__find_end(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
1013           _RandomAccessIterator2 __first2, _RandomAccessIterator2 __last2, _BinaryPredicate __pred,
1014           random_access_iterator_tag, random_access_iterator_tag)
1015{
1016    // Take advantage of knowing source and pattern lengths.  Stop short when source is smaller than pattern
1017    typename iterator_traits<_RandomAccessIterator2>::difference_type __len2 = __last2 - __first2;
1018    if (__len2 == 0)
1019        return __last1;
1020    typename iterator_traits<_RandomAccessIterator1>::difference_type __len1 = __last1 - __first1;
1021    if (__len1 < __len2)
1022        return __last1;
1023    const _RandomAccessIterator1 __s = __first1 + (__len2 - 1);  // End of pattern match can't go before here
1024    _RandomAccessIterator1 __l1 = __last1;
1025    _RandomAccessIterator2 __l2 = __last2;
1026    --__l2;
1027    while (true)
1028    {
1029        while (true)
1030        {
1031            if (__s == __l1)
1032                return __last1;
1033            if (__pred(*--__l1, *__l2))
1034                break;
1035        }
1036        _RandomAccessIterator1 __m1 = __l1;
1037        _RandomAccessIterator2 __m2 = __l2;
1038        while (true)
1039        {
1040            if (__m2 == __first2)
1041                return __m1;
1042                                 // no need to check range on __m1 because __s guarantees we have enough source
1043            if (!__pred(*--__m1, *--__m2))
1044            {
1045                break;
1046            }
1047        }
1048    }
1049}
1050
1051template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1052_LIBCPP_NODISCARD_EXT inline
1053_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1054_ForwardIterator1
1055find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1056         _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred)
1057{
1058    return _VSTD::__find_end<typename add_lvalue_reference<_BinaryPredicate>::type>
1059                         (__first1, __last1, __first2, __last2, __pred,
1060                          typename iterator_traits<_ForwardIterator1>::iterator_category(),
1061                          typename iterator_traits<_ForwardIterator2>::iterator_category());
1062}
1063
1064template <class _ForwardIterator1, class _ForwardIterator2>
1065_LIBCPP_NODISCARD_EXT inline
1066_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1067_ForwardIterator1
1068find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1069         _ForwardIterator2 __first2, _ForwardIterator2 __last2)
1070{
1071    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1072    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1073    return _VSTD::find_end(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
1074}
1075
1076// find_first_of
1077
1078template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1079_LIBCPP_CONSTEXPR_AFTER_CXX11 _ForwardIterator1
1080__find_first_of_ce(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1081              _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred)
1082{
1083    for (; __first1 != __last1; ++__first1)
1084        for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
1085            if (__pred(*__first1, *__j))
1086                return __first1;
1087    return __last1;
1088}
1089
1090
1091template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1092_LIBCPP_NODISCARD_EXT inline
1093_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1094_ForwardIterator1
1095find_first_of(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1096              _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred)
1097{
1098    return _VSTD::__find_first_of_ce(__first1, __last1, __first2, __last2, __pred);
1099}
1100
1101template <class _ForwardIterator1, class _ForwardIterator2>
1102_LIBCPP_NODISCARD_EXT inline
1103_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1104_ForwardIterator1
1105find_first_of(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1106              _ForwardIterator2 __first2, _ForwardIterator2 __last2)
1107{
1108    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1109    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1110    return _VSTD::__find_first_of_ce(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
1111}
1112
1113// adjacent_find
1114
1115template <class _ForwardIterator, class _BinaryPredicate>
1116_LIBCPP_NODISCARD_EXT inline
1117_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1118_ForwardIterator
1119adjacent_find(_ForwardIterator __first, _ForwardIterator __last, _BinaryPredicate __pred)
1120{
1121    if (__first != __last)
1122    {
1123        _ForwardIterator __i = __first;
1124        while (++__i != __last)
1125        {
1126            if (__pred(*__first, *__i))
1127                return __first;
1128            __first = __i;
1129        }
1130    }
1131    return __last;
1132}
1133
1134template <class _ForwardIterator>
1135_LIBCPP_NODISCARD_EXT inline
1136_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1137_ForwardIterator
1138adjacent_find(_ForwardIterator __first, _ForwardIterator __last)
1139{
1140    typedef typename iterator_traits<_ForwardIterator>::value_type __v;
1141    return _VSTD::adjacent_find(__first, __last, __equal_to<__v>());
1142}
1143
1144// count
1145
1146template <class _InputIterator, class _Tp>
1147_LIBCPP_NODISCARD_EXT inline
1148_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1149typename iterator_traits<_InputIterator>::difference_type
1150count(_InputIterator __first, _InputIterator __last, const _Tp& __value_)
1151{
1152    typename iterator_traits<_InputIterator>::difference_type __r(0);
1153    for (; __first != __last; ++__first)
1154        if (*__first == __value_)
1155            ++__r;
1156    return __r;
1157}
1158
1159// count_if
1160
1161template <class _InputIterator, class _Predicate>
1162_LIBCPP_NODISCARD_EXT inline
1163_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1164typename iterator_traits<_InputIterator>::difference_type
1165count_if(_InputIterator __first, _InputIterator __last, _Predicate __pred)
1166{
1167    typename iterator_traits<_InputIterator>::difference_type __r(0);
1168    for (; __first != __last; ++__first)
1169        if (__pred(*__first))
1170            ++__r;
1171    return __r;
1172}
1173
1174// mismatch
1175
1176template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
1177_LIBCPP_NODISCARD_EXT inline
1178_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1179pair<_InputIterator1, _InputIterator2>
1180mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1181         _InputIterator2 __first2, _BinaryPredicate __pred)
1182{
1183    for (; __first1 != __last1; ++__first1, (void) ++__first2)
1184        if (!__pred(*__first1, *__first2))
1185            break;
1186    return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
1187}
1188
1189template <class _InputIterator1, class _InputIterator2>
1190_LIBCPP_NODISCARD_EXT inline
1191_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1192pair<_InputIterator1, _InputIterator2>
1193mismatch(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2)
1194{
1195    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
1196    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
1197    return _VSTD::mismatch(__first1, __last1, __first2, __equal_to<__v1, __v2>());
1198}
1199
1200#if _LIBCPP_STD_VER > 11
1201template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
1202_LIBCPP_NODISCARD_EXT inline
1203_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1204pair<_InputIterator1, _InputIterator2>
1205mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1206         _InputIterator2 __first2, _InputIterator2 __last2,
1207         _BinaryPredicate __pred)
1208{
1209    for (; __first1 != __last1 && __first2 != __last2; ++__first1, (void) ++__first2)
1210        if (!__pred(*__first1, *__first2))
1211            break;
1212    return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
1213}
1214
1215template <class _InputIterator1, class _InputIterator2>
1216_LIBCPP_NODISCARD_EXT inline
1217_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1218pair<_InputIterator1, _InputIterator2>
1219mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1220         _InputIterator2 __first2, _InputIterator2 __last2)
1221{
1222    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
1223    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
1224    return _VSTD::mismatch(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
1225}
1226#endif
1227
1228// equal
1229
1230template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
1231_LIBCPP_NODISCARD_EXT inline
1232_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1233bool
1234equal(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _BinaryPredicate __pred)
1235{
1236    for (; __first1 != __last1; ++__first1, (void) ++__first2)
1237        if (!__pred(*__first1, *__first2))
1238            return false;
1239    return true;
1240}
1241
1242template <class _InputIterator1, class _InputIterator2>
1243_LIBCPP_NODISCARD_EXT inline
1244_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1245bool
1246equal(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2)
1247{
1248    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
1249    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
1250    return _VSTD::equal(__first1, __last1, __first2, __equal_to<__v1, __v2>());
1251}
1252
1253#if _LIBCPP_STD_VER > 11
1254template <class _BinaryPredicate, class _InputIterator1, class _InputIterator2>
1255inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1256bool
1257__equal(_InputIterator1 __first1, _InputIterator1 __last1,
1258        _InputIterator2 __first2, _InputIterator2 __last2, _BinaryPredicate __pred,
1259        input_iterator_tag, input_iterator_tag )
1260{
1261    for (; __first1 != __last1 && __first2 != __last2; ++__first1, (void) ++__first2)
1262        if (!__pred(*__first1, *__first2))
1263            return false;
1264    return __first1 == __last1 && __first2 == __last2;
1265}
1266
1267template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
1268inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1269bool
1270__equal(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
1271        _RandomAccessIterator2 __first2, _RandomAccessIterator2 __last2, _BinaryPredicate __pred,
1272      random_access_iterator_tag, random_access_iterator_tag )
1273{
1274    if ( _VSTD::distance(__first1, __last1) != _VSTD::distance(__first2, __last2))
1275        return false;
1276    return _VSTD::equal<_RandomAccessIterator1, _RandomAccessIterator2,
1277                        typename add_lvalue_reference<_BinaryPredicate>::type>
1278                       (__first1, __last1, __first2, __pred );
1279}
1280
1281template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
1282_LIBCPP_NODISCARD_EXT inline
1283_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1284bool
1285equal(_InputIterator1 __first1, _InputIterator1 __last1,
1286      _InputIterator2 __first2, _InputIterator2 __last2, _BinaryPredicate __pred )
1287{
1288    return _VSTD::__equal<typename add_lvalue_reference<_BinaryPredicate>::type>
1289       (__first1, __last1, __first2, __last2, __pred,
1290        typename iterator_traits<_InputIterator1>::iterator_category(),
1291        typename iterator_traits<_InputIterator2>::iterator_category());
1292}
1293
1294template <class _InputIterator1, class _InputIterator2>
1295_LIBCPP_NODISCARD_EXT inline
1296_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1297bool
1298equal(_InputIterator1 __first1, _InputIterator1 __last1,
1299      _InputIterator2 __first2, _InputIterator2 __last2)
1300{
1301    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
1302    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
1303    return _VSTD::__equal(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>(),
1304        typename iterator_traits<_InputIterator1>::iterator_category(),
1305        typename iterator_traits<_InputIterator2>::iterator_category());
1306}
1307#endif
1308
1309// is_permutation
1310
1311template<class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1312_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
1313is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1314               _ForwardIterator2 __first2, _BinaryPredicate __pred)
1315{
1316//  shorten sequences as much as possible by lopping of any equal prefix
1317    for (; __first1 != __last1; ++__first1, (void) ++__first2)
1318        if (!__pred(*__first1, *__first2))
1319            break;
1320    if (__first1 == __last1)
1321        return true;
1322
1323//  __first1 != __last1 && *__first1 != *__first2
1324    typedef typename iterator_traits<_ForwardIterator1>::difference_type _D1;
1325    _D1 __l1 = _VSTD::distance(__first1, __last1);
1326    if (__l1 == _D1(1))
1327        return false;
1328    _ForwardIterator2 __last2 = _VSTD::next(__first2, __l1);
1329    // For each element in [f1, l1) see if there are the same number of
1330    //    equal elements in [f2, l2)
1331    for (_ForwardIterator1 __i = __first1; __i != __last1; ++__i)
1332    {
1333    //  Have we already counted the number of *__i in [f1, l1)?
1334        _ForwardIterator1 __match = __first1;
1335        for (; __match != __i; ++__match)
1336            if (__pred(*__match, *__i))
1337                break;
1338        if (__match == __i) {
1339            // Count number of *__i in [f2, l2)
1340            _D1 __c2 = 0;
1341            for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
1342                if (__pred(*__i, *__j))
1343                    ++__c2;
1344            if (__c2 == 0)
1345                return false;
1346            // Count number of *__i in [__i, l1) (we can start with 1)
1347            _D1 __c1 = 1;
1348            for (_ForwardIterator1 __j = _VSTD::next(__i); __j != __last1; ++__j)
1349                if (__pred(*__i, *__j))
1350                    ++__c1;
1351            if (__c1 != __c2)
1352                return false;
1353        }
1354    }
1355    return true;
1356}
1357
1358template<class _ForwardIterator1, class _ForwardIterator2>
1359_LIBCPP_NODISCARD_EXT inline
1360_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1361bool
1362is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1363               _ForwardIterator2 __first2)
1364{
1365    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1366    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1367    return _VSTD::is_permutation(__first1, __last1, __first2, __equal_to<__v1, __v2>());
1368}
1369
1370#if _LIBCPP_STD_VER > 11
1371template<class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
1372_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
1373__is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1374                 _ForwardIterator2 __first2, _ForwardIterator2 __last2,
1375                 _BinaryPredicate __pred,
1376                 forward_iterator_tag, forward_iterator_tag )
1377{
1378//  shorten sequences as much as possible by lopping of any equal prefix
1379    for (; __first1 != __last1 && __first2 != __last2; ++__first1, (void) ++__first2)
1380        if (!__pred(*__first1, *__first2))
1381            break;
1382    if (__first1 == __last1)
1383        return __first2 == __last2;
1384    else if (__first2 == __last2)
1385        return false;
1386
1387    typedef typename iterator_traits<_ForwardIterator1>::difference_type _D1;
1388    _D1 __l1 = _VSTD::distance(__first1, __last1);
1389
1390    typedef typename iterator_traits<_ForwardIterator2>::difference_type _D2;
1391    _D2 __l2 = _VSTD::distance(__first2, __last2);
1392    if (__l1 != __l2)
1393        return false;
1394
1395    // For each element in [f1, l1) see if there are the same number of
1396    //    equal elements in [f2, l2)
1397    for (_ForwardIterator1 __i = __first1; __i != __last1; ++__i)
1398    {
1399    //  Have we already counted the number of *__i in [f1, l1)?
1400        _ForwardIterator1 __match = __first1;
1401        for (; __match != __i; ++__match)
1402            if (__pred(*__match, *__i))
1403                break;
1404        if (__match == __i) {
1405            // Count number of *__i in [f2, l2)
1406            _D1 __c2 = 0;
1407            for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
1408                if (__pred(*__i, *__j))
1409                    ++__c2;
1410            if (__c2 == 0)
1411                return false;
1412            // Count number of *__i in [__i, l1) (we can start with 1)
1413            _D1 __c1 = 1;
1414            for (_ForwardIterator1 __j = _VSTD::next(__i); __j != __last1; ++__j)
1415                if (__pred(*__i, *__j))
1416                    ++__c1;
1417            if (__c1 != __c2)
1418                return false;
1419        }
1420    }
1421    return true;
1422}
1423
1424template<class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
1425_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
1426__is_permutation(_RandomAccessIterator1 __first1, _RandomAccessIterator2 __last1,
1427               _RandomAccessIterator1 __first2, _RandomAccessIterator2 __last2,
1428               _BinaryPredicate __pred,
1429               random_access_iterator_tag, random_access_iterator_tag )
1430{
1431    if ( _VSTD::distance(__first1, __last1) != _VSTD::distance(__first2, __last2))
1432        return false;
1433    return _VSTD::is_permutation<_RandomAccessIterator1, _RandomAccessIterator2,
1434                                 typename add_lvalue_reference<_BinaryPredicate>::type>
1435                                (__first1, __last1, __first2, __pred );
1436}
1437
1438template<class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1439_LIBCPP_NODISCARD_EXT inline
1440_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1441bool
1442is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1443               _ForwardIterator2 __first2, _ForwardIterator2 __last2,
1444               _BinaryPredicate __pred )
1445{
1446    return _VSTD::__is_permutation<typename add_lvalue_reference<_BinaryPredicate>::type>
1447       (__first1, __last1, __first2, __last2, __pred,
1448        typename iterator_traits<_ForwardIterator1>::iterator_category(),
1449        typename iterator_traits<_ForwardIterator2>::iterator_category());
1450}
1451
1452template<class _ForwardIterator1, class _ForwardIterator2>
1453_LIBCPP_NODISCARD_EXT inline
1454_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1455bool
1456is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1457               _ForwardIterator2 __first2, _ForwardIterator2 __last2)
1458{
1459    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1460    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1461    return _VSTD::__is_permutation(__first1, __last1, __first2, __last2,
1462        __equal_to<__v1, __v2>(),
1463        typename iterator_traits<_ForwardIterator1>::iterator_category(),
1464        typename iterator_traits<_ForwardIterator2>::iterator_category());
1465}
1466#endif
1467
1468// search
1469// __search is in <functional>
1470
1471template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1472_LIBCPP_NODISCARD_EXT inline
1473_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1474_ForwardIterator1
1475search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1476       _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred)
1477{
1478    return _VSTD::__search<typename add_lvalue_reference<_BinaryPredicate>::type>
1479                         (__first1, __last1, __first2, __last2, __pred,
1480                          typename iterator_traits<_ForwardIterator1>::iterator_category(),
1481                          typename iterator_traits<_ForwardIterator2>::iterator_category())
1482            .first;
1483}
1484
1485template <class _ForwardIterator1, class _ForwardIterator2>
1486_LIBCPP_NODISCARD_EXT inline
1487_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1488_ForwardIterator1
1489search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1490       _ForwardIterator2 __first2, _ForwardIterator2 __last2)
1491{
1492    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1493    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1494    return _VSTD::search(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
1495}
1496
1497
1498#if _LIBCPP_STD_VER > 14
1499template <class _ForwardIterator, class _Searcher>
1500_LIBCPP_NODISCARD_EXT _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1501_ForwardIterator search(_ForwardIterator __f, _ForwardIterator __l, const _Searcher &__s)
1502{ return __s(__f, __l).first; }
1503#endif
1504
1505// search_n
1506
1507template <class _BinaryPredicate, class _ForwardIterator, class _Size, class _Tp>
1508_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
1509__search_n(_ForwardIterator __first, _ForwardIterator __last,
1510           _Size __count, const _Tp& __value_, _BinaryPredicate __pred, forward_iterator_tag)
1511{
1512    if (__count <= 0)
1513        return __first;
1514    while (true)
1515    {
1516        // Find first element in sequence that matchs __value_, with a mininum of loop checks
1517        while (true)
1518        {
1519            if (__first == __last)  // return __last if no element matches __value_
1520                return __last;
1521            if (__pred(*__first, __value_))
1522                break;
1523            ++__first;
1524        }
1525        // *__first matches __value_, now match elements after here
1526        _ForwardIterator __m = __first;
1527        _Size __c(0);
1528        while (true)
1529        {
1530            if (++__c == __count)  // If pattern exhausted, __first is the answer (works for 1 element pattern)
1531                return __first;
1532            if (++__m == __last)  // Otherwise if source exhaused, pattern not found
1533                return __last;
1534            if (!__pred(*__m, __value_))  // if there is a mismatch, restart with a new __first
1535            {
1536                __first = __m;
1537                ++__first;
1538                break;
1539            }  // else there is a match, check next elements
1540        }
1541    }
1542}
1543
1544template <class _BinaryPredicate, class _RandomAccessIterator, class _Size, class _Tp>
1545_LIBCPP_CONSTEXPR_AFTER_CXX17 _RandomAccessIterator
1546__search_n(_RandomAccessIterator __first, _RandomAccessIterator __last,
1547           _Size __count, const _Tp& __value_, _BinaryPredicate __pred, random_access_iterator_tag)
1548{
1549    if (__count <= 0)
1550        return __first;
1551    _Size __len = static_cast<_Size>(__last - __first);
1552    if (__len < __count)
1553        return __last;
1554    const _RandomAccessIterator __s = __last - (__count - 1);  // Start of pattern match can't go beyond here
1555    while (true)
1556    {
1557        // Find first element in sequence that matchs __value_, with a mininum of loop checks
1558        while (true)
1559        {
1560            if (__first >= __s)  // return __last if no element matches __value_
1561                return __last;
1562            if (__pred(*__first, __value_))
1563                break;
1564            ++__first;
1565        }
1566        // *__first matches __value_, now match elements after here
1567        _RandomAccessIterator __m = __first;
1568        _Size __c(0);
1569        while (true)
1570        {
1571            if (++__c == __count)  // If pattern exhausted, __first is the answer (works for 1 element pattern)
1572                return __first;
1573             ++__m;          // no need to check range on __m because __s guarantees we have enough source
1574            if (!__pred(*__m, __value_))  // if there is a mismatch, restart with a new __first
1575            {
1576                __first = __m;
1577                ++__first;
1578                break;
1579            }  // else there is a match, check next elements
1580        }
1581    }
1582}
1583
1584template <class _ForwardIterator, class _Size, class _Tp, class _BinaryPredicate>
1585_LIBCPP_NODISCARD_EXT inline
1586_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1587_ForwardIterator
1588search_n(_ForwardIterator __first, _ForwardIterator __last,
1589         _Size __count, const _Tp& __value_, _BinaryPredicate __pred)
1590{
1591    return _VSTD::__search_n<typename add_lvalue_reference<_BinaryPredicate>::type>
1592           (__first, __last, __convert_to_integral(__count), __value_, __pred,
1593           typename iterator_traits<_ForwardIterator>::iterator_category());
1594}
1595
1596template <class _ForwardIterator, class _Size, class _Tp>
1597_LIBCPP_NODISCARD_EXT inline
1598_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1599_ForwardIterator
1600search_n(_ForwardIterator __first, _ForwardIterator __last, _Size __count, const _Tp& __value_)
1601{
1602    typedef typename iterator_traits<_ForwardIterator>::value_type __v;
1603    return _VSTD::search_n(__first, __last, __convert_to_integral(__count),
1604                           __value_, __equal_to<__v, _Tp>());
1605}
1606
1607// copy
1608template <class _Iter>
1609inline _LIBCPP_INLINE_VISIBILITY
1610_Iter
1611__unwrap_iter(_Iter __i)
1612{
1613    return __i;
1614}
1615
1616template <class _Tp>
1617inline _LIBCPP_INLINE_VISIBILITY
1618typename enable_if
1619<
1620    is_trivially_copy_assignable<_Tp>::value,
1621    _Tp*
1622>::type
1623__unwrap_iter(move_iterator<_Tp*> __i)
1624{
1625    return __i.base();
1626}
1627
1628#if _LIBCPP_DEBUG_LEVEL < 2
1629
1630template <class _Tp>
1631inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
1632typename enable_if
1633<
1634    is_trivially_copy_assignable<_Tp>::value,
1635    _Tp*
1636>::type
1637__unwrap_iter(__wrap_iter<_Tp*> __i)
1638{
1639    return __i.base();
1640}
1641
1642template <class _Tp>
1643inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
1644typename enable_if
1645<
1646    is_trivially_copy_assignable<_Tp>::value,
1647    const _Tp*
1648>::type
1649__unwrap_iter(__wrap_iter<const _Tp*> __i)
1650{
1651    return __i.base();
1652}
1653
1654#else
1655
1656template <class _Tp>
1657inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
1658typename enable_if
1659<
1660    is_trivially_copy_assignable<_Tp>::value,
1661    __wrap_iter<_Tp*>
1662>::type
1663__unwrap_iter(__wrap_iter<_Tp*> __i)
1664{
1665    return __i;
1666}
1667
1668#endif  // _LIBCPP_DEBUG_LEVEL < 2
1669
1670template <class _InputIterator, class _OutputIterator>
1671inline _LIBCPP_INLINE_VISIBILITY
1672_OutputIterator
1673__copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1674{
1675    for (; __first != __last; ++__first, (void) ++__result)
1676        *__result = *__first;
1677    return __result;
1678}
1679
1680template <class _Tp, class _Up>
1681inline _LIBCPP_INLINE_VISIBILITY
1682typename enable_if
1683<
1684    is_same<typename remove_const<_Tp>::type, _Up>::value &&
1685    is_trivially_copy_assignable<_Up>::value,
1686    _Up*
1687>::type
1688__copy(_Tp* __first, _Tp* __last, _Up* __result)
1689{
1690    const size_t __n = static_cast<size_t>(__last - __first);
1691    if (__n > 0)
1692        _VSTD::memmove(__result, __first, __n * sizeof(_Up));
1693    return __result + __n;
1694}
1695
1696template <class _InputIterator, class _OutputIterator>
1697inline _LIBCPP_INLINE_VISIBILITY
1698_OutputIterator
1699copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1700{
1701    return _VSTD::__copy(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
1702}
1703
1704// copy_backward
1705
1706template <class _BidirectionalIterator, class _OutputIterator>
1707inline _LIBCPP_INLINE_VISIBILITY
1708_OutputIterator
1709__copy_backward(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
1710{
1711    while (__first != __last)
1712        *--__result = *--__last;
1713    return __result;
1714}
1715
1716template <class _Tp, class _Up>
1717inline _LIBCPP_INLINE_VISIBILITY
1718typename enable_if
1719<
1720    is_same<typename remove_const<_Tp>::type, _Up>::value &&
1721    is_trivially_copy_assignable<_Up>::value,
1722    _Up*
1723>::type
1724__copy_backward(_Tp* __first, _Tp* __last, _Up* __result)
1725{
1726    const size_t __n = static_cast<size_t>(__last - __first);
1727    if (__n > 0)
1728    {
1729        __result -= __n;
1730        _VSTD::memmove(__result, __first, __n * sizeof(_Up));
1731    }
1732    return __result;
1733}
1734
1735template <class _BidirectionalIterator1, class _BidirectionalIterator2>
1736inline _LIBCPP_INLINE_VISIBILITY
1737_BidirectionalIterator2
1738copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
1739              _BidirectionalIterator2 __result)
1740{
1741    return _VSTD::__copy_backward(__unwrap_iter(__first),
1742                                  __unwrap_iter(__last),
1743                                  __unwrap_iter(__result));
1744}
1745
1746// copy_if
1747
1748template<class _InputIterator, class _OutputIterator, class _Predicate>
1749inline _LIBCPP_INLINE_VISIBILITY
1750_OutputIterator
1751copy_if(_InputIterator __first, _InputIterator __last,
1752        _OutputIterator __result, _Predicate __pred)
1753{
1754    for (; __first != __last; ++__first)
1755    {
1756        if (__pred(*__first))
1757        {
1758            *__result = *__first;
1759            ++__result;
1760        }
1761    }
1762    return __result;
1763}
1764
1765// copy_n
1766
1767template<class _InputIterator, class _Size, class _OutputIterator>
1768inline _LIBCPP_INLINE_VISIBILITY
1769typename enable_if
1770<
1771    __is_input_iterator<_InputIterator>::value &&
1772   !__is_random_access_iterator<_InputIterator>::value,
1773    _OutputIterator
1774>::type
1775copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
1776{
1777    typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;
1778    _IntegralSize __n = __orig_n;
1779    if (__n > 0)
1780    {
1781        *__result = *__first;
1782        ++__result;
1783        for (--__n; __n > 0; --__n)
1784        {
1785            ++__first;
1786            *__result = *__first;
1787            ++__result;
1788        }
1789    }
1790    return __result;
1791}
1792
1793template<class _InputIterator, class _Size, class _OutputIterator>
1794inline _LIBCPP_INLINE_VISIBILITY
1795typename enable_if
1796<
1797    __is_random_access_iterator<_InputIterator>::value,
1798    _OutputIterator
1799>::type
1800copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
1801{
1802    typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;
1803    _IntegralSize __n = __orig_n;
1804    return _VSTD::copy(__first, __first + __n, __result);
1805}
1806
1807// move
1808
1809template <class _InputIterator, class _OutputIterator>
1810inline _LIBCPP_INLINE_VISIBILITY
1811_OutputIterator
1812__move(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1813{
1814    for (; __first != __last; ++__first, (void) ++__result)
1815        *__result = _VSTD::move(*__first);
1816    return __result;
1817}
1818
1819template <class _Tp, class _Up>
1820inline _LIBCPP_INLINE_VISIBILITY
1821typename enable_if
1822<
1823    is_same<typename remove_const<_Tp>::type, _Up>::value &&
1824    is_trivially_copy_assignable<_Up>::value,
1825    _Up*
1826>::type
1827__move(_Tp* __first, _Tp* __last, _Up* __result)
1828{
1829    const size_t __n = static_cast<size_t>(__last - __first);
1830    if (__n > 0)
1831        _VSTD::memmove(__result, __first, __n * sizeof(_Up));
1832    return __result + __n;
1833}
1834
1835template <class _InputIterator, class _OutputIterator>
1836inline _LIBCPP_INLINE_VISIBILITY
1837_OutputIterator
1838move(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1839{
1840    return _VSTD::__move(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
1841}
1842
1843// move_backward
1844
1845template <class _InputIterator, class _OutputIterator>
1846inline _LIBCPP_INLINE_VISIBILITY
1847_OutputIterator
1848__move_backward(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1849{
1850    while (__first != __last)
1851        *--__result = _VSTD::move(*--__last);
1852    return __result;
1853}
1854
1855template <class _Tp, class _Up>
1856inline _LIBCPP_INLINE_VISIBILITY
1857typename enable_if
1858<
1859    is_same<typename remove_const<_Tp>::type, _Up>::value &&
1860    is_trivially_copy_assignable<_Up>::value,
1861    _Up*
1862>::type
1863__move_backward(_Tp* __first, _Tp* __last, _Up* __result)
1864{
1865    const size_t __n = static_cast<size_t>(__last - __first);
1866    if (__n > 0)
1867    {
1868        __result -= __n;
1869        _VSTD::memmove(__result, __first, __n * sizeof(_Up));
1870    }
1871    return __result;
1872}
1873
1874template <class _BidirectionalIterator1, class _BidirectionalIterator2>
1875inline _LIBCPP_INLINE_VISIBILITY
1876_BidirectionalIterator2
1877move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
1878              _BidirectionalIterator2 __result)
1879{
1880    return _VSTD::__move_backward(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
1881}
1882
1883// iter_swap
1884
1885// moved to <type_traits> for better swap / noexcept support
1886
1887// transform
1888
1889template <class _InputIterator, class _OutputIterator, class _UnaryOperation>
1890inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1891_OutputIterator
1892transform(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _UnaryOperation __op)
1893{
1894    for (; __first != __last; ++__first, (void) ++__result)
1895        *__result = __op(*__first);
1896    return __result;
1897}
1898
1899template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _BinaryOperation>
1900inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1901_OutputIterator
1902transform(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2,
1903          _OutputIterator __result, _BinaryOperation __binary_op)
1904{
1905    for (; __first1 != __last1; ++__first1, (void) ++__first2, ++__result)
1906        *__result = __binary_op(*__first1, *__first2);
1907    return __result;
1908}
1909
1910// replace
1911
1912template <class _ForwardIterator, class _Tp>
1913inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1914void
1915replace(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __old_value, const _Tp& __new_value)
1916{
1917    for (; __first != __last; ++__first)
1918        if (*__first == __old_value)
1919            *__first = __new_value;
1920}
1921
1922// replace_if
1923
1924template <class _ForwardIterator, class _Predicate, class _Tp>
1925inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1926void
1927replace_if(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred, const _Tp& __new_value)
1928{
1929    for (; __first != __last; ++__first)
1930        if (__pred(*__first))
1931            *__first = __new_value;
1932}
1933
1934// replace_copy
1935
1936template <class _InputIterator, class _OutputIterator, class _Tp>
1937inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1938_OutputIterator
1939replace_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result,
1940             const _Tp& __old_value, const _Tp& __new_value)
1941{
1942    for (; __first != __last; ++__first, (void) ++__result)
1943        if (*__first == __old_value)
1944            *__result = __new_value;
1945        else
1946            *__result = *__first;
1947    return __result;
1948}
1949
1950// replace_copy_if
1951
1952template <class _InputIterator, class _OutputIterator, class _Predicate, class _Tp>
1953inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1954_OutputIterator
1955replace_copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator __result,
1956                _Predicate __pred, const _Tp& __new_value)
1957{
1958    for (; __first != __last; ++__first, (void) ++__result)
1959        if (__pred(*__first))
1960            *__result = __new_value;
1961        else
1962            *__result = *__first;
1963    return __result;
1964}
1965
1966// fill_n
1967
1968template <class _OutputIterator, class _Size, class _Tp>
1969inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1970_OutputIterator
1971__fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
1972{
1973    for (; __n > 0; ++__first, (void) --__n)
1974        *__first = __value_;
1975    return __first;
1976}
1977
1978template <class _OutputIterator, class _Size, class _Tp>
1979inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1980_OutputIterator
1981fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
1982{
1983   return _VSTD::__fill_n(__first, __convert_to_integral(__n), __value_);
1984}
1985
1986// fill
1987
1988template <class _ForwardIterator, class _Tp>
1989inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1990void
1991__fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, forward_iterator_tag)
1992{
1993    for (; __first != __last; ++__first)
1994        *__first = __value_;
1995}
1996
1997template <class _RandomAccessIterator, class _Tp>
1998inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1999void
2000__fill(_RandomAccessIterator __first, _RandomAccessIterator __last, const _Tp& __value_, random_access_iterator_tag)
2001{
2002    _VSTD::fill_n(__first, __last - __first, __value_);
2003}
2004
2005template <class _ForwardIterator, class _Tp>
2006inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2007void
2008fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
2009{
2010    _VSTD::__fill(__first, __last, __value_, typename iterator_traits<_ForwardIterator>::iterator_category());
2011}
2012
2013// generate
2014
2015template <class _ForwardIterator, class _Generator>
2016inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2017void
2018generate(_ForwardIterator __first, _ForwardIterator __last, _Generator __gen)
2019{
2020    for (; __first != __last; ++__first)
2021        *__first = __gen();
2022}
2023
2024// generate_n
2025
2026template <class _OutputIterator, class _Size, class _Generator>
2027inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2028_OutputIterator
2029generate_n(_OutputIterator __first, _Size __orig_n, _Generator __gen)
2030{
2031    typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;
2032    _IntegralSize __n = __orig_n;
2033    for (; __n > 0; ++__first, (void) --__n)
2034        *__first = __gen();
2035    return __first;
2036}
2037
2038// remove
2039
2040template <class _ForwardIterator, class _Tp>
2041_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
2042remove(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
2043{
2044    __first = _VSTD::find(__first, __last, __value_);
2045    if (__first != __last)
2046    {
2047        _ForwardIterator __i = __first;
2048        while (++__i != __last)
2049        {
2050            if (!(*__i == __value_))
2051            {
2052                *__first = _VSTD::move(*__i);
2053                ++__first;
2054            }
2055        }
2056    }
2057    return __first;
2058}
2059
2060// remove_if
2061
2062template <class _ForwardIterator, class _Predicate>
2063_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
2064remove_if(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
2065{
2066    __first = _VSTD::find_if<_ForwardIterator, typename add_lvalue_reference<_Predicate>::type>
2067                           (__first, __last, __pred);
2068    if (__first != __last)
2069    {
2070        _ForwardIterator __i = __first;
2071        while (++__i != __last)
2072        {
2073            if (!__pred(*__i))
2074            {
2075                *__first = _VSTD::move(*__i);
2076                ++__first;
2077            }
2078        }
2079    }
2080    return __first;
2081}
2082
2083// remove_copy
2084
2085template <class _InputIterator, class _OutputIterator, class _Tp>
2086inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2087_OutputIterator
2088remove_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result, const _Tp& __value_)
2089{
2090    for (; __first != __last; ++__first)
2091    {
2092        if (!(*__first == __value_))
2093        {
2094            *__result = *__first;
2095            ++__result;
2096        }
2097    }
2098    return __result;
2099}
2100
2101// remove_copy_if
2102
2103template <class _InputIterator, class _OutputIterator, class _Predicate>
2104inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2105_OutputIterator
2106remove_copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _Predicate __pred)
2107{
2108    for (; __first != __last; ++__first)
2109    {
2110        if (!__pred(*__first))
2111        {
2112            *__result = *__first;
2113            ++__result;
2114        }
2115    }
2116    return __result;
2117}
2118
2119// unique
2120
2121template <class _ForwardIterator, class _BinaryPredicate>
2122_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
2123unique(_ForwardIterator __first, _ForwardIterator __last, _BinaryPredicate __pred)
2124{
2125    __first = _VSTD::adjacent_find<_ForwardIterator, typename add_lvalue_reference<_BinaryPredicate>::type>
2126                                 (__first, __last, __pred);
2127    if (__first != __last)
2128    {
2129        // ...  a  a  ?  ...
2130        //      f     i
2131        _ForwardIterator __i = __first;
2132        for (++__i; ++__i != __last;)
2133            if (!__pred(*__first, *__i))
2134                *++__first = _VSTD::move(*__i);
2135        ++__first;
2136    }
2137    return __first;
2138}
2139
2140template <class _ForwardIterator>
2141_LIBCPP_NODISCARD_EXT inline
2142_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2143_ForwardIterator
2144unique(_ForwardIterator __first, _ForwardIterator __last)
2145{
2146    typedef typename iterator_traits<_ForwardIterator>::value_type __v;
2147    return _VSTD::unique(__first, __last, __equal_to<__v>());
2148}
2149
2150// unique_copy
2151
2152template <class _BinaryPredicate, class _InputIterator, class _OutputIterator>
2153_LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator
2154__unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _BinaryPredicate __pred,
2155              input_iterator_tag, output_iterator_tag)
2156{
2157    if (__first != __last)
2158    {
2159        typename iterator_traits<_InputIterator>::value_type __t(*__first);
2160        *__result = __t;
2161        ++__result;
2162        while (++__first != __last)
2163        {
2164            if (!__pred(__t, *__first))
2165            {
2166                __t = *__first;
2167                *__result = __t;
2168                ++__result;
2169            }
2170        }
2171    }
2172    return __result;
2173}
2174
2175template <class _BinaryPredicate, class _ForwardIterator, class _OutputIterator>
2176_LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator
2177__unique_copy(_ForwardIterator __first, _ForwardIterator __last, _OutputIterator __result, _BinaryPredicate __pred,
2178              forward_iterator_tag, output_iterator_tag)
2179{
2180    if (__first != __last)
2181    {
2182        _ForwardIterator __i = __first;
2183        *__result = *__i;
2184        ++__result;
2185        while (++__first != __last)
2186        {
2187            if (!__pred(*__i, *__first))
2188            {
2189                *__result = *__first;
2190                ++__result;
2191                __i = __first;
2192            }
2193        }
2194    }
2195    return __result;
2196}
2197
2198template <class _BinaryPredicate, class _InputIterator, class _ForwardIterator>
2199_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
2200__unique_copy(_InputIterator __first, _InputIterator __last, _ForwardIterator __result, _BinaryPredicate __pred,
2201              input_iterator_tag, forward_iterator_tag)
2202{
2203    if (__first != __last)
2204    {
2205        *__result = *__first;
2206        while (++__first != __last)
2207            if (!__pred(*__result, *__first))
2208                *++__result = *__first;
2209        ++__result;
2210    }
2211    return __result;
2212}
2213
2214template <class _InputIterator, class _OutputIterator, class _BinaryPredicate>
2215inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2216_OutputIterator
2217unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _BinaryPredicate __pred)
2218{
2219    return _VSTD::__unique_copy<typename add_lvalue_reference<_BinaryPredicate>::type>
2220                              (__first, __last, __result, __pred,
2221                               typename iterator_traits<_InputIterator>::iterator_category(),
2222                               typename iterator_traits<_OutputIterator>::iterator_category());
2223}
2224
2225template <class _InputIterator, class _OutputIterator>
2226inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2227_OutputIterator
2228unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
2229{
2230    typedef typename iterator_traits<_InputIterator>::value_type __v;
2231    return _VSTD::unique_copy(__first, __last, __result, __equal_to<__v>());
2232}
2233
2234// reverse
2235
2236template <class _BidirectionalIterator>
2237inline _LIBCPP_INLINE_VISIBILITY
2238void
2239__reverse(_BidirectionalIterator __first, _BidirectionalIterator __last, bidirectional_iterator_tag)
2240{
2241    while (__first != __last)
2242    {
2243        if (__first == --__last)
2244            break;
2245        _VSTD::iter_swap(__first, __last);
2246        ++__first;
2247    }
2248}
2249
2250template <class _RandomAccessIterator>
2251inline _LIBCPP_INLINE_VISIBILITY
2252void
2253__reverse(_RandomAccessIterator __first, _RandomAccessIterator __last, random_access_iterator_tag)
2254{
2255    if (__first != __last)
2256        for (; __first < --__last; ++__first)
2257            _VSTD::iter_swap(__first, __last);
2258}
2259
2260template <class _BidirectionalIterator>
2261inline _LIBCPP_INLINE_VISIBILITY
2262void
2263reverse(_BidirectionalIterator __first, _BidirectionalIterator __last)
2264{
2265    _VSTD::__reverse(__first, __last, typename iterator_traits<_BidirectionalIterator>::iterator_category());
2266}
2267
2268// reverse_copy
2269
2270template <class _BidirectionalIterator, class _OutputIterator>
2271inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2272_OutputIterator
2273reverse_copy(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
2274{
2275    for (; __first != __last; ++__result)
2276        *__result = *--__last;
2277    return __result;
2278}
2279
2280// rotate
2281
2282template <class _ForwardIterator>
2283_ForwardIterator
2284__rotate_left(_ForwardIterator __first, _ForwardIterator __last)
2285{
2286    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
2287    value_type __tmp = _VSTD::move(*__first);
2288    _ForwardIterator __lm1 = _VSTD::move(_VSTD::next(__first), __last, __first);
2289    *__lm1 = _VSTD::move(__tmp);
2290    return __lm1;
2291}
2292
2293template <class _BidirectionalIterator>
2294_BidirectionalIterator
2295__rotate_right(_BidirectionalIterator __first, _BidirectionalIterator __last)
2296{
2297    typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
2298    _BidirectionalIterator __lm1 = _VSTD::prev(__last);
2299    value_type __tmp = _VSTD::move(*__lm1);
2300    _BidirectionalIterator __fp1 = _VSTD::move_backward(__first, __lm1, __last);
2301    *__first = _VSTD::move(__tmp);
2302    return __fp1;
2303}
2304
2305template <class _ForwardIterator>
2306_ForwardIterator
2307__rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
2308{
2309    _ForwardIterator __i = __middle;
2310    while (true)
2311    {
2312        swap(*__first, *__i);
2313        ++__first;
2314        if (++__i == __last)
2315            break;
2316        if (__first == __middle)
2317            __middle = __i;
2318    }
2319    _ForwardIterator __r = __first;
2320    if (__first != __middle)
2321    {
2322        __i = __middle;
2323        while (true)
2324        {
2325            swap(*__first, *__i);
2326            ++__first;
2327            if (++__i == __last)
2328            {
2329                if (__first == __middle)
2330                    break;
2331                __i = __middle;
2332            }
2333            else if (__first == __middle)
2334                __middle = __i;
2335        }
2336    }
2337    return __r;
2338}
2339
2340template<typename _Integral>
2341inline _LIBCPP_INLINE_VISIBILITY
2342_Integral
2343__algo_gcd(_Integral __x, _Integral __y)
2344{
2345    do
2346    {
2347        _Integral __t = __x % __y;
2348        __x = __y;
2349        __y = __t;
2350    } while (__y);
2351    return __x;
2352}
2353
2354template<typename _RandomAccessIterator>
2355_RandomAccessIterator
2356__rotate_gcd(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last)
2357{
2358    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
2359    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
2360
2361    const difference_type __m1 = __middle - __first;
2362    const difference_type __m2 = __last - __middle;
2363    if (__m1 == __m2)
2364    {
2365        _VSTD::swap_ranges(__first, __middle, __middle);
2366        return __middle;
2367    }
2368    const difference_type __g = _VSTD::__algo_gcd(__m1, __m2);
2369    for (_RandomAccessIterator __p = __first + __g; __p != __first;)
2370    {
2371        value_type __t(_VSTD::move(*--__p));
2372        _RandomAccessIterator __p1 = __p;
2373        _RandomAccessIterator __p2 = __p1 + __m1;
2374        do
2375        {
2376            *__p1 = _VSTD::move(*__p2);
2377            __p1 = __p2;
2378            const difference_type __d = __last - __p2;
2379            if (__m1 < __d)
2380                __p2 += __m1;
2381            else
2382                __p2 = __first + (__m1 - __d);
2383        } while (__p2 != __p);
2384        *__p1 = _VSTD::move(__t);
2385    }
2386    return __first + __m2;
2387}
2388
2389template <class _ForwardIterator>
2390inline _LIBCPP_INLINE_VISIBILITY
2391_ForwardIterator
2392__rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last,
2393         _VSTD::forward_iterator_tag)
2394{
2395    typedef typename _VSTD::iterator_traits<_ForwardIterator>::value_type value_type;
2396    if (_VSTD::is_trivially_move_assignable<value_type>::value)
2397    {
2398        if (_VSTD::next(__first) == __middle)
2399            return _VSTD::__rotate_left(__first, __last);
2400    }
2401    return _VSTD::__rotate_forward(__first, __middle, __last);
2402}
2403
2404template <class _BidirectionalIterator>
2405inline _LIBCPP_INLINE_VISIBILITY
2406_BidirectionalIterator
2407__rotate(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
2408         _VSTD::bidirectional_iterator_tag)
2409{
2410    typedef typename _VSTD::iterator_traits<_BidirectionalIterator>::value_type value_type;
2411    if (_VSTD::is_trivially_move_assignable<value_type>::value)
2412    {
2413        if (_VSTD::next(__first) == __middle)
2414            return _VSTD::__rotate_left(__first, __last);
2415        if (_VSTD::next(__middle) == __last)
2416            return _VSTD::__rotate_right(__first, __last);
2417    }
2418    return _VSTD::__rotate_forward(__first, __middle, __last);
2419}
2420
2421template <class _RandomAccessIterator>
2422inline _LIBCPP_INLINE_VISIBILITY
2423_RandomAccessIterator
2424__rotate(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last,
2425         _VSTD::random_access_iterator_tag)
2426{
2427    typedef typename _VSTD::iterator_traits<_RandomAccessIterator>::value_type value_type;
2428    if (_VSTD::is_trivially_move_assignable<value_type>::value)
2429    {
2430        if (_VSTD::next(__first) == __middle)
2431            return _VSTD::__rotate_left(__first, __last);
2432        if (_VSTD::next(__middle) == __last)
2433            return _VSTD::__rotate_right(__first, __last);
2434        return _VSTD::__rotate_gcd(__first, __middle, __last);
2435    }
2436    return _VSTD::__rotate_forward(__first, __middle, __last);
2437}
2438
2439template <class _ForwardIterator>
2440inline _LIBCPP_INLINE_VISIBILITY
2441_ForwardIterator
2442rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
2443{
2444    if (__first == __middle)
2445        return __last;
2446    if (__middle == __last)
2447        return __first;
2448    return _VSTD::__rotate(__first, __middle, __last,
2449                           typename _VSTD::iterator_traits<_ForwardIterator>::iterator_category());
2450}
2451
2452// rotate_copy
2453
2454template <class _ForwardIterator, class _OutputIterator>
2455inline _LIBCPP_INLINE_VISIBILITY
2456_OutputIterator
2457rotate_copy(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last, _OutputIterator __result)
2458{
2459    return _VSTD::copy(__first, __middle, _VSTD::copy(__middle, __last, __result));
2460}
2461
2462// min_element
2463
2464template <class _ForwardIterator, class _Compare>
2465_LIBCPP_NODISCARD_EXT inline
2466_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2467_ForwardIterator
2468min_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
2469{
2470    static_assert(__is_forward_iterator<_ForwardIterator>::value,
2471        "std::min_element requires a ForwardIterator");
2472    if (__first != __last)
2473    {
2474        _ForwardIterator __i = __first;
2475        while (++__i != __last)
2476            if (__comp(*__i, *__first))
2477                __first = __i;
2478    }
2479    return __first;
2480}
2481
2482template <class _ForwardIterator>
2483_LIBCPP_NODISCARD_EXT inline
2484_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2485_ForwardIterator
2486min_element(_ForwardIterator __first, _ForwardIterator __last)
2487{
2488    return _VSTD::min_element(__first, __last,
2489              __less<typename iterator_traits<_ForwardIterator>::value_type>());
2490}
2491
2492// min
2493
2494template <class _Tp, class _Compare>
2495_LIBCPP_NODISCARD_EXT inline
2496_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2497const _Tp&
2498min(const _Tp& __a, const _Tp& __b, _Compare __comp)
2499{
2500    return __comp(__b, __a) ? __b : __a;
2501}
2502
2503template <class _Tp>
2504_LIBCPP_NODISCARD_EXT inline
2505_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2506const _Tp&
2507min(const _Tp& __a, const _Tp& __b)
2508{
2509    return _VSTD::min(__a, __b, __less<_Tp>());
2510}
2511
2512#ifndef _LIBCPP_CXX03_LANG
2513
2514template<class _Tp, class _Compare>
2515_LIBCPP_NODISCARD_EXT inline
2516_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2517_Tp
2518min(initializer_list<_Tp> __t, _Compare __comp)
2519{
2520    return *_VSTD::min_element(__t.begin(), __t.end(), __comp);
2521}
2522
2523template<class _Tp>
2524_LIBCPP_NODISCARD_EXT inline
2525_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2526_Tp
2527min(initializer_list<_Tp> __t)
2528{
2529    return *_VSTD::min_element(__t.begin(), __t.end(), __less<_Tp>());
2530}
2531
2532#endif  // _LIBCPP_CXX03_LANG
2533
2534// max_element
2535
2536template <class _ForwardIterator, class _Compare>
2537_LIBCPP_NODISCARD_EXT inline
2538_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2539_ForwardIterator
2540max_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
2541{
2542    static_assert(__is_forward_iterator<_ForwardIterator>::value,
2543        "std::max_element requires a ForwardIterator");
2544    if (__first != __last)
2545    {
2546        _ForwardIterator __i = __first;
2547        while (++__i != __last)
2548            if (__comp(*__first, *__i))
2549                __first = __i;
2550    }
2551    return __first;
2552}
2553
2554
2555template <class _ForwardIterator>
2556_LIBCPP_NODISCARD_EXT inline
2557_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2558_ForwardIterator
2559max_element(_ForwardIterator __first, _ForwardIterator __last)
2560{
2561    return _VSTD::max_element(__first, __last,
2562              __less<typename iterator_traits<_ForwardIterator>::value_type>());
2563}
2564
2565// max
2566
2567template <class _Tp, class _Compare>
2568_LIBCPP_NODISCARD_EXT inline
2569_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2570const _Tp&
2571max(const _Tp& __a, const _Tp& __b, _Compare __comp)
2572{
2573    return __comp(__a, __b) ? __b : __a;
2574}
2575
2576template <class _Tp>
2577_LIBCPP_NODISCARD_EXT inline
2578_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2579const _Tp&
2580max(const _Tp& __a, const _Tp& __b)
2581{
2582    return _VSTD::max(__a, __b, __less<_Tp>());
2583}
2584
2585#ifndef _LIBCPP_CXX03_LANG
2586
2587template<class _Tp, class _Compare>
2588_LIBCPP_NODISCARD_EXT inline
2589_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2590_Tp
2591max(initializer_list<_Tp> __t, _Compare __comp)
2592{
2593    return *_VSTD::max_element(__t.begin(), __t.end(), __comp);
2594}
2595
2596template<class _Tp>
2597_LIBCPP_NODISCARD_EXT inline
2598_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2599_Tp
2600max(initializer_list<_Tp> __t)
2601{
2602    return *_VSTD::max_element(__t.begin(), __t.end(), __less<_Tp>());
2603}
2604
2605#endif  // _LIBCPP_CXX03_LANG
2606
2607#if _LIBCPP_STD_VER > 14
2608// clamp
2609template<class _Tp, class _Compare>
2610_LIBCPP_NODISCARD_EXT inline
2611_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
2612const _Tp&
2613clamp(const _Tp& __v, const _Tp& __lo, const _Tp& __hi, _Compare __comp)
2614{
2615    _LIBCPP_ASSERT(!__comp(__hi, __lo), "Bad bounds passed to std::clamp");
2616    return __comp(__v, __lo) ? __lo : __comp(__hi, __v) ? __hi : __v;
2617
2618}
2619
2620template<class _Tp>
2621_LIBCPP_NODISCARD_EXT inline
2622_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
2623const _Tp&
2624clamp(const _Tp& __v, const _Tp& __lo, const _Tp& __hi)
2625{
2626    return _VSTD::clamp(__v, __lo, __hi, __less<_Tp>());
2627}
2628#endif
2629
2630// minmax_element
2631
2632template <class _ForwardIterator, class _Compare>
2633_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX11
2634std::pair<_ForwardIterator, _ForwardIterator>
2635minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
2636{
2637  static_assert(__is_forward_iterator<_ForwardIterator>::value,
2638        "std::minmax_element requires a ForwardIterator");
2639  std::pair<_ForwardIterator, _ForwardIterator> __result(__first, __first);
2640  if (__first != __last)
2641  {
2642      if (++__first != __last)
2643      {
2644          if (__comp(*__first, *__result.first))
2645              __result.first = __first;
2646          else
2647              __result.second = __first;
2648          while (++__first != __last)
2649          {
2650              _ForwardIterator __i = __first;
2651              if (++__first == __last)
2652              {
2653                  if (__comp(*__i, *__result.first))
2654                      __result.first = __i;
2655                  else if (!__comp(*__i, *__result.second))
2656                      __result.second = __i;
2657                  break;
2658              }
2659              else
2660              {
2661                  if (__comp(*__first, *__i))
2662                  {
2663                      if (__comp(*__first, *__result.first))
2664                          __result.first = __first;
2665                      if (!__comp(*__i, *__result.second))
2666                          __result.second = __i;
2667                  }
2668                  else
2669                  {
2670                      if (__comp(*__i, *__result.first))
2671                          __result.first = __i;
2672                      if (!__comp(*__first, *__result.second))
2673                          __result.second = __first;
2674                  }
2675              }
2676          }
2677      }
2678  }
2679  return __result;
2680}
2681
2682template <class _ForwardIterator>
2683_LIBCPP_NODISCARD_EXT inline
2684_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2685std::pair<_ForwardIterator, _ForwardIterator>
2686minmax_element(_ForwardIterator __first, _ForwardIterator __last)
2687{
2688    return _VSTD::minmax_element(__first, __last,
2689              __less<typename iterator_traits<_ForwardIterator>::value_type>());
2690}
2691
2692// minmax
2693
2694template<class _Tp, class _Compare>
2695_LIBCPP_NODISCARD_EXT inline
2696_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2697pair<const _Tp&, const _Tp&>
2698minmax(const _Tp& __a, const _Tp& __b, _Compare __comp)
2699{
2700    return __comp(__b, __a) ? pair<const _Tp&, const _Tp&>(__b, __a) :
2701                              pair<const _Tp&, const _Tp&>(__a, __b);
2702}
2703
2704template<class _Tp>
2705_LIBCPP_NODISCARD_EXT inline
2706_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2707pair<const _Tp&, const _Tp&>
2708minmax(const _Tp& __a, const _Tp& __b)
2709{
2710    return _VSTD::minmax(__a, __b, __less<_Tp>());
2711}
2712
2713#ifndef _LIBCPP_CXX03_LANG
2714
2715template<class _Tp, class _Compare>
2716_LIBCPP_NODISCARD_EXT inline
2717_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2718pair<_Tp, _Tp>
2719minmax(initializer_list<_Tp> __t, _Compare __comp)
2720{
2721    typedef typename initializer_list<_Tp>::const_iterator _Iter;
2722    _Iter __first = __t.begin();
2723    _Iter __last  = __t.end();
2724    std::pair<_Tp, _Tp> __result(*__first, *__first);
2725
2726    ++__first;
2727    if (__t.size() % 2 == 0)
2728    {
2729        if (__comp(*__first,  __result.first))
2730            __result.first  = *__first;
2731        else
2732            __result.second = *__first;
2733        ++__first;
2734    }
2735
2736    while (__first != __last)
2737    {
2738        _Tp __prev = *__first++;
2739        if (__comp(*__first, __prev)) {
2740            if ( __comp(*__first, __result.first)) __result.first  = *__first;
2741            if (!__comp(__prev, __result.second))  __result.second = __prev;
2742            }
2743        else {
2744            if ( __comp(__prev, __result.first))    __result.first  = __prev;
2745            if (!__comp(*__first, __result.second)) __result.second = *__first;
2746            }
2747
2748        __first++;
2749    }
2750    return __result;
2751}
2752
2753template<class _Tp>
2754_LIBCPP_NODISCARD_EXT inline
2755_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2756pair<_Tp, _Tp>
2757minmax(initializer_list<_Tp> __t)
2758{
2759    return _VSTD::minmax(__t, __less<_Tp>());
2760}
2761
2762#endif  // _LIBCPP_CXX03_LANG
2763
2764// random_shuffle
2765
2766// __independent_bits_engine
2767
2768template <unsigned long long _Xp, size_t _Rp>
2769struct __log2_imp
2770{
2771    static const size_t value = _Xp & ((unsigned long long)(1) << _Rp) ? _Rp
2772                                           : __log2_imp<_Xp, _Rp - 1>::value;
2773};
2774
2775template <unsigned long long _Xp>
2776struct __log2_imp<_Xp, 0>
2777{
2778    static const size_t value = 0;
2779};
2780
2781template <size_t _Rp>
2782struct __log2_imp<0, _Rp>
2783{
2784    static const size_t value = _Rp + 1;
2785};
2786
2787template <class _UIntType, _UIntType _Xp>
2788struct __log2
2789{
2790    static const size_t value = __log2_imp<_Xp,
2791                                         sizeof(_UIntType) * __CHAR_BIT__ - 1>::value;
2792};
2793
2794template<class _Engine, class _UIntType>
2795class __independent_bits_engine
2796{
2797public:
2798    // types
2799    typedef _UIntType result_type;
2800
2801private:
2802    typedef typename _Engine::result_type _Engine_result_type;
2803    typedef typename conditional
2804        <
2805            sizeof(_Engine_result_type) <= sizeof(result_type),
2806                result_type,
2807                _Engine_result_type
2808        >::type _Working_result_type;
2809
2810    _Engine& __e_;
2811    size_t __w_;
2812    size_t __w0_;
2813    size_t __n_;
2814    size_t __n0_;
2815    _Working_result_type __y0_;
2816    _Working_result_type __y1_;
2817    _Engine_result_type __mask0_;
2818    _Engine_result_type __mask1_;
2819
2820#ifdef _LIBCPP_CXX03_LANG
2821    static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min
2822                                          + _Working_result_type(1);
2823#else
2824    static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min()
2825                                                      + _Working_result_type(1);
2826#endif
2827    static _LIBCPP_CONSTEXPR const size_t __m = __log2<_Working_result_type, _Rp>::value;
2828    static _LIBCPP_CONSTEXPR const size_t _WDt = numeric_limits<_Working_result_type>::digits;
2829    static _LIBCPP_CONSTEXPR const size_t _EDt = numeric_limits<_Engine_result_type>::digits;
2830
2831public:
2832    // constructors and seeding functions
2833    __independent_bits_engine(_Engine& __e, size_t __w);
2834
2835    // generating functions
2836    result_type operator()() {return __eval(integral_constant<bool, _Rp != 0>());}
2837
2838private:
2839    result_type __eval(false_type);
2840    result_type __eval(true_type);
2841};
2842
2843template<class _Engine, class _UIntType>
2844__independent_bits_engine<_Engine, _UIntType>
2845    ::__independent_bits_engine(_Engine& __e, size_t __w)
2846        : __e_(__e),
2847          __w_(__w)
2848{
2849    __n_ = __w_ / __m + (__w_ % __m != 0);
2850    __w0_ = __w_ / __n_;
2851    if (_Rp == 0)
2852        __y0_ = _Rp;
2853    else if (__w0_ < _WDt)
2854        __y0_ = (_Rp >> __w0_) << __w0_;
2855    else
2856        __y0_ = 0;
2857    if (_Rp - __y0_ > __y0_ / __n_)
2858    {
2859        ++__n_;
2860        __w0_ = __w_ / __n_;
2861        if (__w0_ < _WDt)
2862            __y0_ = (_Rp >> __w0_) << __w0_;
2863        else
2864            __y0_ = 0;
2865    }
2866    __n0_ = __n_ - __w_ % __n_;
2867    if (__w0_ < _WDt - 1)
2868        __y1_ = (_Rp >> (__w0_ + 1)) << (__w0_ + 1);
2869    else
2870        __y1_ = 0;
2871    __mask0_ = __w0_ > 0 ? _Engine_result_type(~0) >> (_EDt - __w0_) :
2872                          _Engine_result_type(0);
2873    __mask1_ = __w0_ < _EDt - 1 ?
2874                               _Engine_result_type(~0) >> (_EDt - (__w0_ + 1)) :
2875                               _Engine_result_type(~0);
2876}
2877
2878template<class _Engine, class _UIntType>
2879inline
2880_UIntType
2881__independent_bits_engine<_Engine, _UIntType>::__eval(false_type)
2882{
2883    return static_cast<result_type>(__e_() & __mask0_);
2884}
2885
2886template<class _Engine, class _UIntType>
2887_UIntType
2888__independent_bits_engine<_Engine, _UIntType>::__eval(true_type)
2889{
2890    const size_t _WRt = numeric_limits<result_type>::digits;
2891    result_type _Sp = 0;
2892    for (size_t __k = 0; __k < __n0_; ++__k)
2893    {
2894        _Engine_result_type __u;
2895        do
2896        {
2897            __u = __e_() - _Engine::min();
2898        } while (__u >= __y0_);
2899        if (__w0_ < _WRt)
2900            _Sp <<= __w0_;
2901        else
2902            _Sp = 0;
2903        _Sp += __u & __mask0_;
2904    }
2905    for (size_t __k = __n0_; __k < __n_; ++__k)
2906    {
2907        _Engine_result_type __u;
2908        do
2909        {
2910            __u = __e_() - _Engine::min();
2911        } while (__u >= __y1_);
2912        if (__w0_ < _WRt - 1)
2913            _Sp <<= __w0_ + 1;
2914        else
2915            _Sp = 0;
2916        _Sp += __u & __mask1_;
2917    }
2918    return _Sp;
2919}
2920
2921// uniform_int_distribution
2922
2923template<class _IntType = int>
2924class uniform_int_distribution
2925{
2926public:
2927    // types
2928    typedef _IntType result_type;
2929
2930    class param_type
2931    {
2932        result_type __a_;
2933        result_type __b_;
2934    public:
2935        typedef uniform_int_distribution distribution_type;
2936
2937        explicit param_type(result_type __a = 0,
2938                            result_type __b = numeric_limits<result_type>::max())
2939            : __a_(__a), __b_(__b) {}
2940
2941        result_type a() const {return __a_;}
2942        result_type b() const {return __b_;}
2943
2944        friend bool operator==(const param_type& __x, const param_type& __y)
2945            {return __x.__a_ == __y.__a_ && __x.__b_ == __y.__b_;}
2946        friend bool operator!=(const param_type& __x, const param_type& __y)
2947            {return !(__x == __y);}
2948    };
2949
2950private:
2951    param_type __p_;
2952
2953public:
2954    // constructors and reset functions
2955    explicit uniform_int_distribution(result_type __a = 0,
2956                                      result_type __b = numeric_limits<result_type>::max())
2957        : __p_(param_type(__a, __b)) {}
2958    explicit uniform_int_distribution(const param_type& __p) : __p_(__p) {}
2959    void reset() {}
2960
2961    // generating functions
2962    template<class _URNG> result_type operator()(_URNG& __g)
2963        {return (*this)(__g, __p_);}
2964    template<class _URNG> result_type operator()(_URNG& __g, const param_type& __p);
2965
2966    // property functions
2967    result_type a() const {return __p_.a();}
2968    result_type b() const {return __p_.b();}
2969
2970    param_type param() const {return __p_;}
2971    void param(const param_type& __p) {__p_ = __p;}
2972
2973    result_type min() const {return a();}
2974    result_type max() const {return b();}
2975
2976    friend bool operator==(const uniform_int_distribution& __x,
2977                           const uniform_int_distribution& __y)
2978        {return __x.__p_ == __y.__p_;}
2979    friend bool operator!=(const uniform_int_distribution& __x,
2980                           const uniform_int_distribution& __y)
2981            {return !(__x == __y);}
2982};
2983
2984template<class _IntType>
2985template<class _URNG>
2986typename uniform_int_distribution<_IntType>::result_type
2987uniform_int_distribution<_IntType>::operator()(_URNG& __g, const param_type& __p)
2988_LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
2989{
2990    typedef typename conditional<sizeof(result_type) <= sizeof(uint32_t),
2991                                            uint32_t, uint64_t>::type _UIntType;
2992    const _UIntType _Rp = _UIntType(__p.b()) - _UIntType(__p.a()) + _UIntType(1);
2993    if (_Rp == 1)
2994        return __p.a();
2995    const size_t _Dt = numeric_limits<_UIntType>::digits;
2996    typedef __independent_bits_engine<_URNG, _UIntType> _Eng;
2997    if (_Rp == 0)
2998        return static_cast<result_type>(_Eng(__g, _Dt)());
2999    size_t __w = _Dt - __clz(_Rp) - 1;
3000    if ((_Rp & (std::numeric_limits<_UIntType>::max() >> (_Dt - __w))) != 0)
3001        ++__w;
3002    _Eng __e(__g, __w);
3003    _UIntType __u;
3004    do
3005    {
3006        __u = __e();
3007    } while (__u >= _Rp);
3008    return static_cast<result_type>(__u + __p.a());
3009}
3010
3011#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_RANDOM_SHUFFLE) \
3012  || defined(_LIBCPP_BUILDING_LIBRARY)
3013class _LIBCPP_TYPE_VIS __rs_default;
3014
3015_LIBCPP_FUNC_VIS __rs_default __rs_get();
3016
3017class _LIBCPP_TYPE_VIS __rs_default
3018{
3019    static unsigned __c_;
3020
3021    __rs_default();
3022public:
3023    typedef uint_fast32_t result_type;
3024
3025    static const result_type _Min = 0;
3026    static const result_type _Max = 0xFFFFFFFF;
3027
3028    __rs_default(const __rs_default&);
3029    ~__rs_default();
3030
3031    result_type operator()();
3032
3033    static _LIBCPP_CONSTEXPR result_type min() {return _Min;}
3034    static _LIBCPP_CONSTEXPR result_type max() {return _Max;}
3035
3036    friend _LIBCPP_FUNC_VIS __rs_default __rs_get();
3037};
3038
3039_LIBCPP_FUNC_VIS __rs_default __rs_get();
3040
3041template <class _RandomAccessIterator>
3042_LIBCPP_DEPRECATED_IN_CXX14 void
3043random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last)
3044{
3045    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
3046    typedef uniform_int_distribution<ptrdiff_t> _Dp;
3047    typedef typename _Dp::param_type _Pp;
3048    difference_type __d = __last - __first;
3049    if (__d > 1)
3050    {
3051        _Dp __uid;
3052        __rs_default __g = __rs_get();
3053        for (--__last, (void) --__d; __first < __last; ++__first, (void) --__d)
3054        {
3055            difference_type __i = __uid(__g, _Pp(0, __d));
3056            if (__i != difference_type(0))
3057                swap(*__first, *(__first + __i));
3058        }
3059    }
3060}
3061
3062template <class _RandomAccessIterator, class _RandomNumberGenerator>
3063_LIBCPP_DEPRECATED_IN_CXX14 void
3064random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
3065#ifndef _LIBCPP_CXX03_LANG
3066               _RandomNumberGenerator&& __rand)
3067#else
3068               _RandomNumberGenerator& __rand)
3069#endif
3070{
3071    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
3072    difference_type __d = __last - __first;
3073    if (__d > 1)
3074    {
3075        for (--__last; __first < __last; ++__first, (void) --__d)
3076        {
3077            difference_type __i = __rand(__d);
3078            if (__i != difference_type(0))
3079              swap(*__first, *(__first + __i));
3080        }
3081    }
3082}
3083#endif
3084
3085template <class _PopulationIterator, class _SampleIterator, class _Distance,
3086          class _UniformRandomNumberGenerator>
3087_LIBCPP_INLINE_VISIBILITY
3088_SampleIterator __sample(_PopulationIterator __first,
3089                         _PopulationIterator __last, _SampleIterator __output_iter,
3090                         _Distance __n,
3091                         _UniformRandomNumberGenerator & __g,
3092                         input_iterator_tag) {
3093
3094  _Distance __k = 0;
3095  for (; __first != __last && __k < __n; ++__first, (void)++__k)
3096    __output_iter[__k] = *__first;
3097  _Distance __sz = __k;
3098  for (; __first != __last; ++__first, (void)++__k) {
3099    _Distance __r = _VSTD::uniform_int_distribution<_Distance>(0, __k)(__g);
3100    if (__r < __sz)
3101      __output_iter[__r] = *__first;
3102  }
3103  return __output_iter + _VSTD::min(__n, __k);
3104}
3105
3106template <class _PopulationIterator, class _SampleIterator, class _Distance,
3107          class _UniformRandomNumberGenerator>
3108_LIBCPP_INLINE_VISIBILITY
3109_SampleIterator __sample(_PopulationIterator __first,
3110                         _PopulationIterator __last, _SampleIterator __output_iter,
3111                         _Distance __n,
3112                         _UniformRandomNumberGenerator& __g,
3113                         forward_iterator_tag) {
3114  _Distance __unsampled_sz = _VSTD::distance(__first, __last);
3115  for (__n = _VSTD::min(__n, __unsampled_sz); __n != 0; ++__first) {
3116    _Distance __r =
3117        _VSTD::uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);
3118    if (__r < __n) {
3119      *__output_iter++ = *__first;
3120      --__n;
3121    }
3122  }
3123  return __output_iter;
3124}
3125
3126template <class _PopulationIterator, class _SampleIterator, class _Distance,
3127          class _UniformRandomNumberGenerator>
3128_LIBCPP_INLINE_VISIBILITY
3129_SampleIterator __sample(_PopulationIterator __first,
3130                         _PopulationIterator __last, _SampleIterator __output_iter,
3131                         _Distance __n, _UniformRandomNumberGenerator& __g) {
3132  typedef typename iterator_traits<_PopulationIterator>::iterator_category
3133        _PopCategory;
3134  typedef typename iterator_traits<_PopulationIterator>::difference_type
3135        _Difference;
3136  static_assert(__is_forward_iterator<_PopulationIterator>::value ||
3137                __is_random_access_iterator<_SampleIterator>::value,
3138                "SampleIterator must meet the requirements of RandomAccessIterator");
3139  typedef typename common_type<_Distance, _Difference>::type _CommonType;
3140  _LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
3141  return _VSTD::__sample(
3142      __first, __last, __output_iter, _CommonType(__n),
3143      __g, _PopCategory());
3144}
3145
3146#if _LIBCPP_STD_VER > 14
3147template <class _PopulationIterator, class _SampleIterator, class _Distance,
3148          class _UniformRandomNumberGenerator>
3149inline _LIBCPP_INLINE_VISIBILITY
3150_SampleIterator sample(_PopulationIterator __first,
3151                       _PopulationIterator __last, _SampleIterator __output_iter,
3152                       _Distance __n, _UniformRandomNumberGenerator&& __g) {
3153    return _VSTD::__sample(__first, __last, __output_iter, __n, __g);
3154}
3155#endif // _LIBCPP_STD_VER > 14
3156
3157template<class _RandomAccessIterator, class _UniformRandomNumberGenerator>
3158    void shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
3159#ifndef _LIBCPP_CXX03_LANG
3160                 _UniformRandomNumberGenerator&& __g)
3161#else
3162                 _UniformRandomNumberGenerator& __g)
3163#endif
3164{
3165    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
3166    typedef uniform_int_distribution<ptrdiff_t> _Dp;
3167    typedef typename _Dp::param_type _Pp;
3168    difference_type __d = __last - __first;
3169    if (__d > 1)
3170    {
3171        _Dp __uid;
3172        for (--__last, --__d; __first < __last; ++__first, --__d)
3173        {
3174            difference_type __i = __uid(__g, _Pp(0, __d));
3175            if (__i != difference_type(0))
3176                swap(*__first, *(__first + __i));
3177        }
3178    }
3179}
3180
3181template <class _InputIterator, class _Predicate>
3182_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
3183is_partitioned(_InputIterator __first, _InputIterator __last, _Predicate __pred)
3184{
3185    for (; __first != __last; ++__first)
3186        if (!__pred(*__first))
3187            break;
3188    if ( __first == __last )
3189        return true;
3190    ++__first;
3191    for (; __first != __last; ++__first)
3192        if (__pred(*__first))
3193            return false;
3194    return true;
3195}
3196
3197// partition
3198
3199template <class _Predicate, class _ForwardIterator>
3200_ForwardIterator
3201__partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred, forward_iterator_tag)
3202{
3203    while (true)
3204    {
3205        if (__first == __last)
3206            return __first;
3207        if (!__pred(*__first))
3208            break;
3209        ++__first;
3210    }
3211    for (_ForwardIterator __p = __first; ++__p != __last;)
3212    {
3213        if (__pred(*__p))
3214        {
3215            swap(*__first, *__p);
3216            ++__first;
3217        }
3218    }
3219    return __first;
3220}
3221
3222template <class _Predicate, class _BidirectionalIterator>
3223_BidirectionalIterator
3224__partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
3225            bidirectional_iterator_tag)
3226{
3227    while (true)
3228    {
3229        while (true)
3230        {
3231            if (__first == __last)
3232                return __first;
3233            if (!__pred(*__first))
3234                break;
3235            ++__first;
3236        }
3237        do
3238        {
3239            if (__first == --__last)
3240                return __first;
3241        } while (!__pred(*__last));
3242        swap(*__first, *__last);
3243        ++__first;
3244    }
3245}
3246
3247template <class _ForwardIterator, class _Predicate>
3248inline _LIBCPP_INLINE_VISIBILITY
3249_ForwardIterator
3250partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
3251{
3252    return _VSTD::__partition<typename add_lvalue_reference<_Predicate>::type>
3253                            (__first, __last, __pred, typename iterator_traits<_ForwardIterator>::iterator_category());
3254}
3255
3256// partition_copy
3257
3258template <class _InputIterator, class _OutputIterator1,
3259          class _OutputIterator2, class _Predicate>
3260_LIBCPP_CONSTEXPR_AFTER_CXX17 pair<_OutputIterator1, _OutputIterator2>
3261partition_copy(_InputIterator __first, _InputIterator __last,
3262               _OutputIterator1 __out_true, _OutputIterator2 __out_false,
3263               _Predicate __pred)
3264{
3265    for (; __first != __last; ++__first)
3266    {
3267        if (__pred(*__first))
3268        {
3269            *__out_true = *__first;
3270            ++__out_true;
3271        }
3272        else
3273        {
3274            *__out_false = *__first;
3275            ++__out_false;
3276        }
3277    }
3278    return pair<_OutputIterator1, _OutputIterator2>(__out_true, __out_false);
3279}
3280
3281// partition_point
3282
3283template<class _ForwardIterator, class _Predicate>
3284_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
3285partition_point(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
3286{
3287    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
3288    difference_type __len = _VSTD::distance(__first, __last);
3289    while (__len != 0)
3290    {
3291        difference_type __l2 = _VSTD::__half_positive(__len);
3292        _ForwardIterator __m = __first;
3293        _VSTD::advance(__m, __l2);
3294        if (__pred(*__m))
3295        {
3296            __first = ++__m;
3297            __len -= __l2 + 1;
3298        }
3299        else
3300            __len = __l2;
3301    }
3302    return __first;
3303}
3304
3305// stable_partition
3306
3307template <class _Predicate, class _ForwardIterator, class _Distance, class _Pair>
3308_ForwardIterator
3309__stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
3310                   _Distance __len, _Pair __p, forward_iterator_tag __fit)
3311{
3312    // *__first is known to be false
3313    // __len >= 1
3314    if (__len == 1)
3315        return __first;
3316    if (__len == 2)
3317    {
3318        _ForwardIterator __m = __first;
3319        if (__pred(*++__m))
3320        {
3321            swap(*__first, *__m);
3322            return __m;
3323        }
3324        return __first;
3325    }
3326    if (__len <= __p.second)
3327    {   // The buffer is big enough to use
3328        typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
3329        __destruct_n __d(0);
3330        unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
3331        // Move the falses into the temporary buffer, and the trues to the front of the line
3332        // Update __first to always point to the end of the trues
3333        value_type* __t = __p.first;
3334        ::new(__t) value_type(_VSTD::move(*__first));
3335        __d.__incr((value_type*)0);
3336        ++__t;
3337        _ForwardIterator __i = __first;
3338        while (++__i != __last)
3339        {
3340            if (__pred(*__i))
3341            {
3342                *__first = _VSTD::move(*__i);
3343                ++__first;
3344            }
3345            else
3346            {
3347                ::new(__t) value_type(_VSTD::move(*__i));
3348                __d.__incr((value_type*)0);
3349                ++__t;
3350            }
3351        }
3352        // All trues now at start of range, all falses in buffer
3353        // Move falses back into range, but don't mess up __first which points to first false
3354        __i = __first;
3355        for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, ++__i)
3356            *__i = _VSTD::move(*__t2);
3357        // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
3358        return __first;
3359    }
3360    // Else not enough buffer, do in place
3361    // __len >= 3
3362    _ForwardIterator __m = __first;
3363    _Distance __len2 = __len / 2;  // __len2 >= 2
3364    _VSTD::advance(__m, __len2);
3365    // recurse on [__first, __m), *__first know to be false
3366    // F?????????????????
3367    // f       m         l
3368    typedef typename add_lvalue_reference<_Predicate>::type _PredRef;
3369    _ForwardIterator __first_false = __stable_partition<_PredRef>(__first, __m, __pred, __len2, __p, __fit);
3370    // TTTFFFFF??????????
3371    // f  ff   m         l
3372    // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
3373    _ForwardIterator __m1 = __m;
3374    _ForwardIterator __second_false = __last;
3375    _Distance __len_half = __len - __len2;
3376    while (__pred(*__m1))
3377    {
3378        if (++__m1 == __last)
3379            goto __second_half_done;
3380        --__len_half;
3381    }
3382    // TTTFFFFFTTTF??????
3383    // f  ff   m  m1     l
3384    __second_false = __stable_partition<_PredRef>(__m1, __last, __pred, __len_half, __p, __fit);
3385__second_half_done:
3386    // TTTFFFFFTTTTTFFFFF
3387    // f  ff   m    sf   l
3388    return _VSTD::rotate(__first_false, __m, __second_false);
3389    // TTTTTTTTFFFFFFFFFF
3390    //         |
3391}
3392
3393struct __return_temporary_buffer
3394{
3395    template <class _Tp>
3396    _LIBCPP_INLINE_VISIBILITY void operator()(_Tp* __p) const {_VSTD::return_temporary_buffer(__p);}
3397};
3398
3399template <class _Predicate, class _ForwardIterator>
3400_ForwardIterator
3401__stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
3402                   forward_iterator_tag)
3403{
3404    const unsigned __alloc_limit = 3;  // might want to make this a function of trivial assignment
3405    // Either prove all true and return __first or point to first false
3406    while (true)
3407    {
3408        if (__first == __last)
3409            return __first;
3410        if (!__pred(*__first))
3411            break;
3412        ++__first;
3413    }
3414    // We now have a reduced range [__first, __last)
3415    // *__first is known to be false
3416    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
3417    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
3418    difference_type __len = _VSTD::distance(__first, __last);
3419    pair<value_type*, ptrdiff_t> __p(0, 0);
3420    unique_ptr<value_type, __return_temporary_buffer> __h;
3421    if (__len >= __alloc_limit)
3422    {
3423        __p = _VSTD::get_temporary_buffer<value_type>(__len);
3424        __h.reset(__p.first);
3425    }
3426    return __stable_partition<typename add_lvalue_reference<_Predicate>::type>
3427                             (__first, __last, __pred, __len, __p, forward_iterator_tag());
3428}
3429
3430template <class _Predicate, class _BidirectionalIterator, class _Distance, class _Pair>
3431_BidirectionalIterator
3432__stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
3433                   _Distance __len, _Pair __p, bidirectional_iterator_tag __bit)
3434{
3435    // *__first is known to be false
3436    // *__last is known to be true
3437    // __len >= 2
3438    if (__len == 2)
3439    {
3440        swap(*__first, *__last);
3441        return __last;
3442    }
3443    if (__len == 3)
3444    {
3445        _BidirectionalIterator __m = __first;
3446        if (__pred(*++__m))
3447        {
3448            swap(*__first, *__m);
3449            swap(*__m, *__last);
3450            return __last;
3451        }
3452        swap(*__m, *__last);
3453        swap(*__first, *__m);
3454        return __m;
3455    }
3456    if (__len <= __p.second)
3457    {   // The buffer is big enough to use
3458        typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
3459        __destruct_n __d(0);
3460        unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
3461        // Move the falses into the temporary buffer, and the trues to the front of the line
3462        // Update __first to always point to the end of the trues
3463        value_type* __t = __p.first;
3464        ::new(__t) value_type(_VSTD::move(*__first));
3465        __d.__incr((value_type*)0);
3466        ++__t;
3467        _BidirectionalIterator __i = __first;
3468        while (++__i != __last)
3469        {
3470            if (__pred(*__i))
3471            {
3472                *__first = _VSTD::move(*__i);
3473                ++__first;
3474            }
3475            else
3476            {
3477                ::new(__t) value_type(_VSTD::move(*__i));
3478                __d.__incr((value_type*)0);
3479                ++__t;
3480            }
3481        }
3482        // move *__last, known to be true
3483        *__first = _VSTD::move(*__i);
3484        __i = ++__first;
3485        // All trues now at start of range, all falses in buffer
3486        // Move falses back into range, but don't mess up __first which points to first false
3487        for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, ++__i)
3488            *__i = _VSTD::move(*__t2);
3489        // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
3490        return __first;
3491    }
3492    // Else not enough buffer, do in place
3493    // __len >= 4
3494    _BidirectionalIterator __m = __first;
3495    _Distance __len2 = __len / 2;  // __len2 >= 2
3496    _VSTD::advance(__m, __len2);
3497    // recurse on [__first, __m-1], except reduce __m-1 until *(__m-1) is true, *__first know to be false
3498    // F????????????????T
3499    // f       m        l
3500    _BidirectionalIterator __m1 = __m;
3501    _BidirectionalIterator __first_false = __first;
3502    _Distance __len_half = __len2;
3503    while (!__pred(*--__m1))
3504    {
3505        if (__m1 == __first)
3506            goto __first_half_done;
3507        --__len_half;
3508    }
3509    // F???TFFF?????????T
3510    // f   m1  m        l
3511    typedef typename add_lvalue_reference<_Predicate>::type _PredRef;
3512    __first_false = __stable_partition<_PredRef>(__first, __m1, __pred, __len_half, __p, __bit);
3513__first_half_done:
3514    // TTTFFFFF?????????T
3515    // f  ff   m        l
3516    // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
3517    __m1 = __m;
3518    _BidirectionalIterator __second_false = __last;
3519    ++__second_false;
3520    __len_half = __len - __len2;
3521    while (__pred(*__m1))
3522    {
3523        if (++__m1 == __last)
3524            goto __second_half_done;
3525        --__len_half;
3526    }
3527    // TTTFFFFFTTTF?????T
3528    // f  ff   m  m1    l
3529    __second_false = __stable_partition<_PredRef>(__m1, __last, __pred, __len_half, __p, __bit);
3530__second_half_done:
3531    // TTTFFFFFTTTTTFFFFF
3532    // f  ff   m    sf  l
3533    return _VSTD::rotate(__first_false, __m, __second_false);
3534    // TTTTTTTTFFFFFFFFFF
3535    //         |
3536}
3537
3538template <class _Predicate, class _BidirectionalIterator>
3539_BidirectionalIterator
3540__stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
3541                   bidirectional_iterator_tag)
3542{
3543    typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
3544    typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
3545    const difference_type __alloc_limit = 4;  // might want to make this a function of trivial assignment
3546    // Either prove all true and return __first or point to first false
3547    while (true)
3548    {
3549        if (__first == __last)
3550            return __first;
3551        if (!__pred(*__first))
3552            break;
3553        ++__first;
3554    }
3555    // __first points to first false, everything prior to __first is already set.
3556    // Either prove [__first, __last) is all false and return __first, or point __last to last true
3557    do
3558    {
3559        if (__first == --__last)
3560            return __first;
3561    } while (!__pred(*__last));
3562    // We now have a reduced range [__first, __last]
3563    // *__first is known to be false
3564    // *__last is known to be true
3565    // __len >= 2
3566    difference_type __len = _VSTD::distance(__first, __last) + 1;
3567    pair<value_type*, ptrdiff_t> __p(0, 0);
3568    unique_ptr<value_type, __return_temporary_buffer> __h;
3569    if (__len >= __alloc_limit)
3570    {
3571        __p = _VSTD::get_temporary_buffer<value_type>(__len);
3572        __h.reset(__p.first);
3573    }
3574    return __stable_partition<typename add_lvalue_reference<_Predicate>::type>
3575                             (__first, __last, __pred, __len, __p, bidirectional_iterator_tag());
3576}
3577
3578template <class _ForwardIterator, class _Predicate>
3579inline _LIBCPP_INLINE_VISIBILITY
3580_ForwardIterator
3581stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
3582{
3583    return __stable_partition<typename add_lvalue_reference<_Predicate>::type>
3584                             (__first, __last, __pred, typename iterator_traits<_ForwardIterator>::iterator_category());
3585}
3586
3587// is_sorted_until
3588
3589template <class _ForwardIterator, class _Compare>
3590_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
3591is_sorted_until(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
3592{
3593    if (__first != __last)
3594    {
3595        _ForwardIterator __i = __first;
3596        while (++__i != __last)
3597        {
3598            if (__comp(*__i, *__first))
3599                return __i;
3600            __first = __i;
3601        }
3602    }
3603    return __last;
3604}
3605
3606template<class _ForwardIterator>
3607_LIBCPP_NODISCARD_EXT inline
3608_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
3609_ForwardIterator
3610is_sorted_until(_ForwardIterator __first, _ForwardIterator __last)
3611{
3612    return _VSTD::is_sorted_until(__first, __last, __less<typename iterator_traits<_ForwardIterator>::value_type>());
3613}
3614
3615// is_sorted
3616
3617template <class _ForwardIterator, class _Compare>
3618_LIBCPP_NODISCARD_EXT inline
3619_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
3620bool
3621is_sorted(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
3622{
3623    return _VSTD::is_sorted_until(__first, __last, __comp) == __last;
3624}
3625
3626template<class _ForwardIterator>
3627_LIBCPP_NODISCARD_EXT inline
3628_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
3629bool
3630is_sorted(_ForwardIterator __first, _ForwardIterator __last)
3631{
3632    return _VSTD::is_sorted(__first, __last, __less<typename iterator_traits<_ForwardIterator>::value_type>());
3633}
3634
3635// sort
3636
3637// stable, 2-3 compares, 0-2 swaps
3638
3639template <class _Compare, class _ForwardIterator>
3640unsigned
3641__sort3(_ForwardIterator __x, _ForwardIterator __y, _ForwardIterator __z, _Compare __c)
3642{
3643    unsigned __r = 0;
3644    if (!__c(*__y, *__x))          // if x <= y
3645    {
3646        if (!__c(*__z, *__y))      // if y <= z
3647            return __r;            // x <= y && y <= z
3648                                   // x <= y && y > z
3649        swap(*__y, *__z);          // x <= z && y < z
3650        __r = 1;
3651        if (__c(*__y, *__x))       // if x > y
3652        {
3653            swap(*__x, *__y);      // x < y && y <= z
3654            __r = 2;
3655        }
3656        return __r;                // x <= y && y < z
3657    }
3658    if (__c(*__z, *__y))           // x > y, if y > z
3659    {
3660        swap(*__x, *__z);          // x < y && y < z
3661        __r = 1;
3662        return __r;
3663    }
3664    swap(*__x, *__y);              // x > y && y <= z
3665    __r = 1;                       // x < y && x <= z
3666    if (__c(*__z, *__y))           // if y > z
3667    {
3668        swap(*__y, *__z);          // x <= y && y < z
3669        __r = 2;
3670    }
3671    return __r;
3672}                                  // x <= y && y <= z
3673
3674// stable, 3-6 compares, 0-5 swaps
3675
3676template <class _Compare, class _ForwardIterator>
3677unsigned
3678__sort4(_ForwardIterator __x1, _ForwardIterator __x2, _ForwardIterator __x3,
3679            _ForwardIterator __x4, _Compare __c)
3680{
3681    unsigned __r = __sort3<_Compare>(__x1, __x2, __x3, __c);
3682    if (__c(*__x4, *__x3))
3683    {
3684        swap(*__x3, *__x4);
3685        ++__r;
3686        if (__c(*__x3, *__x2))
3687        {
3688            swap(*__x2, *__x3);
3689            ++__r;
3690            if (__c(*__x2, *__x1))
3691            {
3692                swap(*__x1, *__x2);
3693                ++__r;
3694            }
3695        }
3696    }
3697    return __r;
3698}
3699
3700// stable, 4-10 compares, 0-9 swaps
3701
3702template <class _Compare, class _ForwardIterator>
3703_LIBCPP_HIDDEN
3704unsigned
3705__sort5(_ForwardIterator __x1, _ForwardIterator __x2, _ForwardIterator __x3,
3706            _ForwardIterator __x4, _ForwardIterator __x5, _Compare __c)
3707{
3708    unsigned __r = __sort4<_Compare>(__x1, __x2, __x3, __x4, __c);
3709    if (__c(*__x5, *__x4))
3710    {
3711        swap(*__x4, *__x5);
3712        ++__r;
3713        if (__c(*__x4, *__x3))
3714        {
3715            swap(*__x3, *__x4);
3716            ++__r;
3717            if (__c(*__x3, *__x2))
3718            {
3719                swap(*__x2, *__x3);
3720                ++__r;
3721                if (__c(*__x2, *__x1))
3722                {
3723                    swap(*__x1, *__x2);
3724                    ++__r;
3725                }
3726            }
3727        }
3728    }
3729    return __r;
3730}
3731
3732// Assumes size > 0
3733template <class _Compare, class _BirdirectionalIterator>
3734void
3735__selection_sort(_BirdirectionalIterator __first, _BirdirectionalIterator __last, _Compare __comp)
3736{
3737    _BirdirectionalIterator __lm1 = __last;
3738    for (--__lm1; __first != __lm1; ++__first)
3739    {
3740        _BirdirectionalIterator __i = _VSTD::min_element<_BirdirectionalIterator,
3741                                                        typename add_lvalue_reference<_Compare>::type>
3742                                                       (__first, __last, __comp);
3743        if (__i != __first)
3744            swap(*__first, *__i);
3745    }
3746}
3747
3748template <class _Compare, class _BirdirectionalIterator>
3749void
3750__insertion_sort(_BirdirectionalIterator __first, _BirdirectionalIterator __last, _Compare __comp)
3751{
3752    typedef typename iterator_traits<_BirdirectionalIterator>::value_type value_type;
3753    if (__first != __last)
3754    {
3755        _BirdirectionalIterator __i = __first;
3756        for (++__i; __i != __last; ++__i)
3757        {
3758            _BirdirectionalIterator __j = __i;
3759            value_type __t(_VSTD::move(*__j));
3760            for (_BirdirectionalIterator __k = __i; __k != __first && __comp(__t,  *--__k); --__j)
3761                *__j = _VSTD::move(*__k);
3762            *__j = _VSTD::move(__t);
3763        }
3764    }
3765}
3766
3767template <class _Compare, class _RandomAccessIterator>
3768void
3769__insertion_sort_3(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
3770{
3771    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
3772    _RandomAccessIterator __j = __first+2;
3773    __sort3<_Compare>(__first, __first+1, __j, __comp);
3774    for (_RandomAccessIterator __i = __j+1; __i != __last; ++__i)
3775    {
3776        if (__comp(*__i, *__j))
3777        {
3778            value_type __t(_VSTD::move(*__i));
3779            _RandomAccessIterator __k = __j;
3780            __j = __i;
3781            do
3782            {
3783                *__j = _VSTD::move(*__k);
3784                __j = __k;
3785            } while (__j != __first && __comp(__t, *--__k));
3786            *__j = _VSTD::move(__t);
3787        }
3788        __j = __i;
3789    }
3790}
3791
3792template <class _Compare, class _RandomAccessIterator>
3793bool
3794__insertion_sort_incomplete(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
3795{
3796    switch (__last - __first)
3797    {
3798    case 0:
3799    case 1:
3800        return true;
3801    case 2:
3802        if (__comp(*--__last, *__first))
3803            swap(*__first, *__last);
3804        return true;
3805    case 3:
3806        _VSTD::__sort3<_Compare>(__first, __first+1, --__last, __comp);
3807        return true;
3808    case 4:
3809        _VSTD::__sort4<_Compare>(__first, __first+1, __first+2, --__last, __comp);
3810        return true;
3811    case 5:
3812        _VSTD::__sort5<_Compare>(__first, __first+1, __first+2, __first+3, --__last, __comp);
3813        return true;
3814    }
3815    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
3816    _RandomAccessIterator __j = __first+2;
3817    __sort3<_Compare>(__first, __first+1, __j, __comp);
3818    const unsigned __limit = 8;
3819    unsigned __count = 0;
3820    for (_RandomAccessIterator __i = __j+1; __i != __last; ++__i)
3821    {
3822        if (__comp(*__i, *__j))
3823        {
3824            value_type __t(_VSTD::move(*__i));
3825            _RandomAccessIterator __k = __j;
3826            __j = __i;
3827            do
3828            {
3829                *__j = _VSTD::move(*__k);
3830                __j = __k;
3831            } while (__j != __first && __comp(__t, *--__k));
3832            *__j = _VSTD::move(__t);
3833            if (++__count == __limit)
3834                return ++__i == __last;
3835        }
3836        __j = __i;
3837    }
3838    return true;
3839}
3840
3841template <class _Compare, class _BirdirectionalIterator>
3842void
3843__insertion_sort_move(_BirdirectionalIterator __first1, _BirdirectionalIterator __last1,
3844                      typename iterator_traits<_BirdirectionalIterator>::value_type* __first2, _Compare __comp)
3845{
3846    typedef typename iterator_traits<_BirdirectionalIterator>::value_type value_type;
3847    if (__first1 != __last1)
3848    {
3849        __destruct_n __d(0);
3850        unique_ptr<value_type, __destruct_n&> __h(__first2, __d);
3851        value_type* __last2 = __first2;
3852        ::new(__last2) value_type(_VSTD::move(*__first1));
3853        __d.__incr((value_type*)0);
3854        for (++__last2; ++__first1 != __last1; ++__last2)
3855        {
3856            value_type* __j2 = __last2;
3857            value_type* __i2 = __j2;
3858            if (__comp(*__first1, *--__i2))
3859            {
3860                ::new(__j2) value_type(_VSTD::move(*__i2));
3861                __d.__incr((value_type*)0);
3862                for (--__j2; __i2 != __first2 && __comp(*__first1,  *--__i2); --__j2)
3863                    *__j2 = _VSTD::move(*__i2);
3864                *__j2 = _VSTD::move(*__first1);
3865            }
3866            else
3867            {
3868                ::new(__j2) value_type(_VSTD::move(*__first1));
3869                __d.__incr((value_type*)0);
3870            }
3871        }
3872        __h.release();
3873    }
3874}
3875
3876template <class _Compare, class _RandomAccessIterator>
3877void
3878__sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
3879{
3880    // _Compare is known to be a reference type
3881    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
3882    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
3883    const difference_type __limit = is_trivially_copy_constructible<value_type>::value &&
3884                                    is_trivially_copy_assignable<value_type>::value ? 30 : 6;
3885    while (true)
3886    {
3887    __restart:
3888        difference_type __len = __last - __first;
3889        switch (__len)
3890        {
3891        case 0:
3892        case 1:
3893            return;
3894        case 2:
3895            if (__comp(*--__last, *__first))
3896                swap(*__first, *__last);
3897            return;
3898        case 3:
3899            _VSTD::__sort3<_Compare>(__first, __first+1, --__last, __comp);
3900            return;
3901        case 4:
3902            _VSTD::__sort4<_Compare>(__first, __first+1, __first+2, --__last, __comp);
3903            return;
3904        case 5:
3905            _VSTD::__sort5<_Compare>(__first, __first+1, __first+2, __first+3, --__last, __comp);
3906            return;
3907        }
3908        if (__len <= __limit)
3909        {
3910            _VSTD::__insertion_sort_3<_Compare>(__first, __last, __comp);
3911            return;
3912        }
3913        // __len > 5
3914        _RandomAccessIterator __m = __first;
3915        _RandomAccessIterator __lm1 = __last;
3916        --__lm1;
3917        unsigned __n_swaps;
3918        {
3919        difference_type __delta;
3920        if (__len >= 1000)
3921        {
3922            __delta = __len/2;
3923            __m += __delta;
3924            __delta /= 2;
3925            __n_swaps = _VSTD::__sort5<_Compare>(__first, __first + __delta, __m, __m+__delta, __lm1, __comp);
3926        }
3927        else
3928        {
3929            __delta = __len/2;
3930            __m += __delta;
3931            __n_swaps = _VSTD::__sort3<_Compare>(__first, __m, __lm1, __comp);
3932        }
3933        }
3934        // *__m is median
3935        // partition [__first, __m) < *__m and *__m <= [__m, __last)
3936        // (this inhibits tossing elements equivalent to __m around unnecessarily)
3937        _RandomAccessIterator __i = __first;
3938        _RandomAccessIterator __j = __lm1;
3939        // j points beyond range to be tested, *__m is known to be <= *__lm1
3940        // The search going up is known to be guarded but the search coming down isn't.
3941        // Prime the downward search with a guard.
3942        if (!__comp(*__i, *__m))  // if *__first == *__m
3943        {
3944            // *__first == *__m, *__first doesn't go in first part
3945            // manually guard downward moving __j against __i
3946            while (true)
3947            {
3948                if (__i == --__j)
3949                {
3950                    // *__first == *__m, *__m <= all other elements
3951                    // Parition instead into [__first, __i) == *__first and *__first < [__i, __last)
3952                    ++__i;  // __first + 1
3953                    __j = __last;
3954                    if (!__comp(*__first, *--__j))  // we need a guard if *__first == *(__last-1)
3955                    {
3956                        while (true)
3957                        {
3958                            if (__i == __j)
3959                                return;  // [__first, __last) all equivalent elements
3960                            if (__comp(*__first, *__i))
3961                            {
3962                                swap(*__i, *__j);
3963                                ++__n_swaps;
3964                                ++__i;
3965                                break;
3966                            }
3967                            ++__i;
3968                        }
3969                    }
3970                    // [__first, __i) == *__first and *__first < [__j, __last) and __j == __last - 1
3971                    if (__i == __j)
3972                        return;
3973                    while (true)
3974                    {
3975                        while (!__comp(*__first, *__i))
3976                            ++__i;
3977                        while (__comp(*__first, *--__j))
3978                            ;
3979                        if (__i >= __j)
3980                            break;
3981                        swap(*__i, *__j);
3982                        ++__n_swaps;
3983                        ++__i;
3984                    }
3985                    // [__first, __i) == *__first and *__first < [__i, __last)
3986                    // The first part is sorted, sort the secod part
3987                    // _VSTD::__sort<_Compare>(__i, __last, __comp);
3988                    __first = __i;
3989                    goto __restart;
3990                }
3991                if (__comp(*__j, *__m))
3992                {
3993                    swap(*__i, *__j);
3994                    ++__n_swaps;
3995                    break;  // found guard for downward moving __j, now use unguarded partition
3996                }
3997            }
3998        }
3999        // It is known that *__i < *__m
4000        ++__i;
4001        // j points beyond range to be tested, *__m is known to be <= *__lm1
4002        // if not yet partitioned...
4003        if (__i < __j)
4004        {
4005            // known that *(__i - 1) < *__m
4006            // known that __i <= __m
4007            while (true)
4008            {
4009                // __m still guards upward moving __i
4010                while (__comp(*__i, *__m))
4011                    ++__i;
4012                // It is now known that a guard exists for downward moving __j
4013                while (!__comp(*--__j, *__m))
4014                    ;
4015                if (__i > __j)
4016                    break;
4017                swap(*__i, *__j);
4018                ++__n_swaps;
4019                // It is known that __m != __j
4020                // If __m just moved, follow it
4021                if (__m == __i)
4022                    __m = __j;
4023                ++__i;
4024            }
4025        }
4026        // [__first, __i) < *__m and *__m <= [__i, __last)
4027        if (__i != __m && __comp(*__m, *__i))
4028        {
4029            swap(*__i, *__m);
4030            ++__n_swaps;
4031        }
4032        // [__first, __i) < *__i and *__i <= [__i+1, __last)
4033        // If we were given a perfect partition, see if insertion sort is quick...
4034        if (__n_swaps == 0)
4035        {
4036            bool __fs = _VSTD::__insertion_sort_incomplete<_Compare>(__first, __i, __comp);
4037            if (_VSTD::__insertion_sort_incomplete<_Compare>(__i+1, __last, __comp))
4038            {
4039                if (__fs)
4040                    return;
4041                __last = __i;
4042                continue;
4043            }
4044            else
4045            {
4046                if (__fs)
4047                {
4048                    __first = ++__i;
4049                    continue;
4050                }
4051            }
4052        }
4053        // sort smaller range with recursive call and larger with tail recursion elimination
4054        if (__i - __first < __last - __i)
4055        {
4056            _VSTD::__sort<_Compare>(__first, __i, __comp);
4057            // _VSTD::__sort<_Compare>(__i+1, __last, __comp);
4058            __first = ++__i;
4059        }
4060        else
4061        {
4062            _VSTD::__sort<_Compare>(__i+1, __last, __comp);
4063            // _VSTD::__sort<_Compare>(__first, __i, __comp);
4064            __last = __i;
4065        }
4066    }
4067}
4068
4069// This forwarder keeps the top call and the recursive calls using the same instantiation, forcing a reference _Compare
4070template <class _RandomAccessIterator, class _Compare>
4071inline _LIBCPP_INLINE_VISIBILITY
4072void
4073sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4074{
4075#ifdef _LIBCPP_DEBUG
4076    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
4077    __debug_less<_Compare> __c(__comp);
4078    __sort<_Comp_ref>(__first, __last, __c);
4079#else  // _LIBCPP_DEBUG
4080    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4081    __sort<_Comp_ref>(__first, __last, __comp);
4082#endif  // _LIBCPP_DEBUG
4083}
4084
4085template <class _RandomAccessIterator>
4086inline _LIBCPP_INLINE_VISIBILITY
4087void
4088sort(_RandomAccessIterator __first, _RandomAccessIterator __last)
4089{
4090    _VSTD::sort(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4091}
4092
4093template <class _Tp>
4094inline _LIBCPP_INLINE_VISIBILITY
4095void
4096sort(_Tp** __first, _Tp** __last)
4097{
4098    _VSTD::sort((size_t*)__first, (size_t*)__last, __less<size_t>());
4099}
4100
4101template <class _Tp>
4102inline _LIBCPP_INLINE_VISIBILITY
4103void
4104sort(__wrap_iter<_Tp*> __first, __wrap_iter<_Tp*> __last)
4105{
4106    _VSTD::sort(__first.base(), __last.base());
4107}
4108
4109template <class _Tp, class _Compare>
4110inline _LIBCPP_INLINE_VISIBILITY
4111void
4112sort(__wrap_iter<_Tp*> __first, __wrap_iter<_Tp*> __last, _Compare __comp)
4113{
4114    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4115    _VSTD::sort<_Tp*, _Comp_ref>(__first.base(), __last.base(), __comp);
4116}
4117
4118_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<char>&, char*>(char*, char*, __less<char>&))
4119_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<wchar_t>&, wchar_t*>(wchar_t*, wchar_t*, __less<wchar_t>&))
4120_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<signed char>&, signed char*>(signed char*, signed char*, __less<signed char>&))
4121_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned char>&, unsigned char*>(unsigned char*, unsigned char*, __less<unsigned char>&))
4122_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<short>&, short*>(short*, short*, __less<short>&))
4123_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned short>&, unsigned short*>(unsigned short*, unsigned short*, __less<unsigned short>&))
4124_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<int>&, int*>(int*, int*, __less<int>&))
4125_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned>&, unsigned*>(unsigned*, unsigned*, __less<unsigned>&))
4126_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<long>&, long*>(long*, long*, __less<long>&))
4127_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned long>&, unsigned long*>(unsigned long*, unsigned long*, __less<unsigned long>&))
4128_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<long long>&, long long*>(long long*, long long*, __less<long long>&))
4129_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned long long>&, unsigned long long*>(unsigned long long*, unsigned long long*, __less<unsigned long long>&))
4130_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<float>&, float*>(float*, float*, __less<float>&))
4131_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<double>&, double*>(double*, double*, __less<double>&))
4132_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<long double>&, long double*>(long double*, long double*, __less<long double>&))
4133
4134_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<char>&, char*>(char*, char*, __less<char>&))
4135_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<wchar_t>&, wchar_t*>(wchar_t*, wchar_t*, __less<wchar_t>&))
4136_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<signed char>&, signed char*>(signed char*, signed char*, __less<signed char>&))
4137_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned char>&, unsigned char*>(unsigned char*, unsigned char*, __less<unsigned char>&))
4138_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<short>&, short*>(short*, short*, __less<short>&))
4139_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned short>&, unsigned short*>(unsigned short*, unsigned short*, __less<unsigned short>&))
4140_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<int>&, int*>(int*, int*, __less<int>&))
4141_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned>&, unsigned*>(unsigned*, unsigned*, __less<unsigned>&))
4142_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<long>&, long*>(long*, long*, __less<long>&))
4143_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned long>&, unsigned long*>(unsigned long*, unsigned long*, __less<unsigned long>&))
4144_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<long long>&, long long*>(long long*, long long*, __less<long long>&))
4145_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned long long>&, unsigned long long*>(unsigned long long*, unsigned long long*, __less<unsigned long long>&))
4146_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<float>&, float*>(float*, float*, __less<float>&))
4147_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<double>&, double*>(double*, double*, __less<double>&))
4148_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<long double>&, long double*>(long double*, long double*, __less<long double>&))
4149
4150_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS unsigned __sort5<__less<long double>&, long double*>(long double*, long double*, long double*, long double*, long double*, __less<long double>&))
4151
4152// lower_bound
4153
4154template <class _Compare, class _ForwardIterator, class _Tp>
4155_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
4156__lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4157{
4158    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
4159    difference_type __len = _VSTD::distance(__first, __last);
4160    while (__len != 0)
4161    {
4162        difference_type __l2 = _VSTD::__half_positive(__len);
4163        _ForwardIterator __m = __first;
4164        _VSTD::advance(__m, __l2);
4165        if (__comp(*__m, __value_))
4166        {
4167            __first = ++__m;
4168            __len -= __l2 + 1;
4169        }
4170        else
4171            __len = __l2;
4172    }
4173    return __first;
4174}
4175
4176template <class _ForwardIterator, class _Tp, class _Compare>
4177_LIBCPP_NODISCARD_EXT inline
4178_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4179_ForwardIterator
4180lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4181{
4182    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4183    return __lower_bound<_Comp_ref>(__first, __last, __value_, __comp);
4184}
4185
4186template <class _ForwardIterator, class _Tp>
4187_LIBCPP_NODISCARD_EXT inline
4188_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4189_ForwardIterator
4190lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
4191{
4192    return _VSTD::lower_bound(__first, __last, __value_,
4193                             __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
4194}
4195
4196// upper_bound
4197
4198template <class _Compare, class _ForwardIterator, class _Tp>
4199_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
4200__upper_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4201{
4202    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
4203    difference_type __len = _VSTD::distance(__first, __last);
4204    while (__len != 0)
4205    {
4206        difference_type __l2 = _VSTD::__half_positive(__len);
4207        _ForwardIterator __m = __first;
4208        _VSTD::advance(__m, __l2);
4209        if (__comp(__value_, *__m))
4210            __len = __l2;
4211        else
4212        {
4213            __first = ++__m;
4214            __len -= __l2 + 1;
4215        }
4216    }
4217    return __first;
4218}
4219
4220template <class _ForwardIterator, class _Tp, class _Compare>
4221_LIBCPP_NODISCARD_EXT inline
4222_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4223_ForwardIterator
4224upper_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4225{
4226    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4227    return __upper_bound<_Comp_ref>(__first, __last, __value_, __comp);
4228}
4229
4230template <class _ForwardIterator, class _Tp>
4231_LIBCPP_NODISCARD_EXT inline
4232_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4233_ForwardIterator
4234upper_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
4235{
4236    return _VSTD::upper_bound(__first, __last, __value_,
4237                             __less<_Tp, typename iterator_traits<_ForwardIterator>::value_type>());
4238}
4239
4240// equal_range
4241
4242template <class _Compare, class _ForwardIterator, class _Tp>
4243_LIBCPP_CONSTEXPR_AFTER_CXX17 pair<_ForwardIterator, _ForwardIterator>
4244__equal_range(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4245{
4246    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
4247    difference_type __len = _VSTD::distance(__first, __last);
4248    while (__len != 0)
4249    {
4250        difference_type __l2 = _VSTD::__half_positive(__len);
4251        _ForwardIterator __m = __first;
4252        _VSTD::advance(__m, __l2);
4253        if (__comp(*__m, __value_))
4254        {
4255            __first = ++__m;
4256            __len -= __l2 + 1;
4257        }
4258        else if (__comp(__value_, *__m))
4259        {
4260            __last = __m;
4261            __len = __l2;
4262        }
4263        else
4264        {
4265            _ForwardIterator __mp1 = __m;
4266            return pair<_ForwardIterator, _ForwardIterator>
4267                   (
4268                      __lower_bound<_Compare>(__first, __m, __value_, __comp),
4269                      __upper_bound<_Compare>(++__mp1, __last, __value_, __comp)
4270                   );
4271        }
4272    }
4273    return pair<_ForwardIterator, _ForwardIterator>(__first, __first);
4274}
4275
4276template <class _ForwardIterator, class _Tp, class _Compare>
4277_LIBCPP_NODISCARD_EXT inline
4278_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4279pair<_ForwardIterator, _ForwardIterator>
4280equal_range(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4281{
4282#ifdef _LIBCPP_DEBUG
4283    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
4284    __debug_less<_Compare> __c(__comp);
4285    return __equal_range<_Comp_ref>(__first, __last, __value_, __c);
4286#else  // _LIBCPP_DEBUG
4287    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4288    return __equal_range<_Comp_ref>(__first, __last, __value_, __comp);
4289#endif  // _LIBCPP_DEBUG
4290}
4291
4292template <class _ForwardIterator, class _Tp>
4293_LIBCPP_NODISCARD_EXT inline
4294_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4295pair<_ForwardIterator, _ForwardIterator>
4296equal_range(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
4297{
4298    return _VSTD::equal_range(__first, __last, __value_,
4299                             __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
4300}
4301
4302// binary_search
4303
4304template <class _Compare, class _ForwardIterator, class _Tp>
4305inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4306bool
4307__binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4308{
4309    __first = __lower_bound<_Compare>(__first, __last, __value_, __comp);
4310    return __first != __last && !__comp(__value_, *__first);
4311}
4312
4313template <class _ForwardIterator, class _Tp, class _Compare>
4314_LIBCPP_NODISCARD_EXT inline
4315_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4316bool
4317binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4318{
4319#ifdef _LIBCPP_DEBUG
4320    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
4321    __debug_less<_Compare> __c(__comp);
4322    return __binary_search<_Comp_ref>(__first, __last, __value_, __c);
4323#else  // _LIBCPP_DEBUG
4324    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4325    return __binary_search<_Comp_ref>(__first, __last, __value_, __comp);
4326#endif  // _LIBCPP_DEBUG
4327}
4328
4329template <class _ForwardIterator, class _Tp>
4330_LIBCPP_NODISCARD_EXT inline
4331_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4332bool
4333binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
4334{
4335    return _VSTD::binary_search(__first, __last, __value_,
4336                             __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
4337}
4338
4339// merge
4340
4341template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
4342_OutputIterator
4343__merge(_InputIterator1 __first1, _InputIterator1 __last1,
4344        _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
4345{
4346    for (; __first1 != __last1; ++__result)
4347    {
4348        if (__first2 == __last2)
4349            return _VSTD::copy(__first1, __last1, __result);
4350        if (__comp(*__first2, *__first1))
4351        {
4352            *__result = *__first2;
4353            ++__first2;
4354        }
4355        else
4356        {
4357            *__result = *__first1;
4358            ++__first1;
4359        }
4360    }
4361    return _VSTD::copy(__first2, __last2, __result);
4362}
4363
4364template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
4365inline _LIBCPP_INLINE_VISIBILITY
4366_OutputIterator
4367merge(_InputIterator1 __first1, _InputIterator1 __last1,
4368      _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
4369{
4370#ifdef _LIBCPP_DEBUG
4371    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
4372    __debug_less<_Compare> __c(__comp);
4373    return _VSTD::__merge<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __c);
4374#else  // _LIBCPP_DEBUG
4375    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4376    return _VSTD::__merge<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
4377#endif  // _LIBCPP_DEBUG
4378}
4379
4380template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
4381inline _LIBCPP_INLINE_VISIBILITY
4382_OutputIterator
4383merge(_InputIterator1 __first1, _InputIterator1 __last1,
4384      _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
4385{
4386    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
4387    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
4388    return merge(__first1, __last1, __first2, __last2, __result, __less<__v1, __v2>());
4389}
4390
4391// inplace_merge
4392
4393template <class _Compare, class _InputIterator1, class _InputIterator2,
4394          class _OutputIterator>
4395void __half_inplace_merge(_InputIterator1 __first1, _InputIterator1 __last1,
4396                          _InputIterator2 __first2, _InputIterator2 __last2,
4397                          _OutputIterator __result, _Compare __comp)
4398{
4399    for (; __first1 != __last1; ++__result)
4400    {
4401        if (__first2 == __last2)
4402        {
4403            _VSTD::move(__first1, __last1, __result);
4404            return;
4405        }
4406
4407        if (__comp(*__first2, *__first1))
4408        {
4409            *__result = _VSTD::move(*__first2);
4410            ++__first2;
4411        }
4412        else
4413        {
4414            *__result = _VSTD::move(*__first1);
4415            ++__first1;
4416        }
4417    }
4418    // __first2 through __last2 are already in the right spot.
4419}
4420
4421template <class _Compare, class _BidirectionalIterator>
4422void
4423__buffered_inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
4424                _Compare __comp, typename iterator_traits<_BidirectionalIterator>::difference_type __len1,
4425                                 typename iterator_traits<_BidirectionalIterator>::difference_type __len2,
4426                typename iterator_traits<_BidirectionalIterator>::value_type* __buff)
4427{
4428    typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
4429    __destruct_n __d(0);
4430    unique_ptr<value_type, __destruct_n&> __h2(__buff, __d);
4431    if (__len1 <= __len2)
4432    {
4433        value_type* __p = __buff;
4434        for (_BidirectionalIterator __i = __first; __i != __middle; __d.__incr((value_type*)0), (void) ++__i, ++__p)
4435            ::new(__p) value_type(_VSTD::move(*__i));
4436        __half_inplace_merge(__buff, __p, __middle, __last, __first, __comp);
4437    }
4438    else
4439    {
4440        value_type* __p = __buff;
4441        for (_BidirectionalIterator __i = __middle; __i != __last; __d.__incr((value_type*)0), (void) ++__i, ++__p)
4442            ::new(__p) value_type(_VSTD::move(*__i));
4443        typedef reverse_iterator<_BidirectionalIterator> _RBi;
4444        typedef reverse_iterator<value_type*> _Rv;
4445        __half_inplace_merge(_Rv(__p), _Rv(__buff),
4446                             _RBi(__middle), _RBi(__first),
4447                             _RBi(__last), __invert<_Compare>(__comp));
4448    }
4449}
4450
4451template <class _Compare, class _BidirectionalIterator>
4452void
4453__inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
4454                _Compare __comp, typename iterator_traits<_BidirectionalIterator>::difference_type __len1,
4455                                 typename iterator_traits<_BidirectionalIterator>::difference_type __len2,
4456                typename iterator_traits<_BidirectionalIterator>::value_type* __buff, ptrdiff_t __buff_size)
4457{
4458    typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
4459    while (true)
4460    {
4461        // if __middle == __last, we're done
4462        if (__len2 == 0)
4463            return;
4464        if (__len1 <= __buff_size || __len2 <= __buff_size)
4465            return __buffered_inplace_merge<_Compare>
4466                   (__first, __middle, __last, __comp, __len1, __len2, __buff);
4467        // shrink [__first, __middle) as much as possible (with no moves), returning if it shrinks to 0
4468        for (; true; ++__first, (void) --__len1)
4469        {
4470            if (__len1 == 0)
4471                return;
4472            if (__comp(*__middle, *__first))
4473                break;
4474        }
4475        // __first < __middle < __last
4476        // *__first > *__middle
4477        // partition [__first, __m1) [__m1, __middle) [__middle, __m2) [__m2, __last) such that
4478        //     all elements in:
4479        //         [__first, __m1)  <= [__middle, __m2)
4480        //         [__middle, __m2) <  [__m1, __middle)
4481        //         [__m1, __middle) <= [__m2, __last)
4482        //     and __m1 or __m2 is in the middle of its range
4483        _BidirectionalIterator __m1;  // "median" of [__first, __middle)
4484        _BidirectionalIterator __m2;  // "median" of [__middle, __last)
4485        difference_type __len11;      // distance(__first, __m1)
4486        difference_type __len21;      // distance(__middle, __m2)
4487        // binary search smaller range
4488        if (__len1 < __len2)
4489        {   // __len >= 1, __len2 >= 2
4490            __len21 = __len2 / 2;
4491            __m2 = __middle;
4492            _VSTD::advance(__m2, __len21);
4493            __m1 = __upper_bound<_Compare>(__first, __middle, *__m2, __comp);
4494            __len11 = _VSTD::distance(__first, __m1);
4495        }
4496        else
4497        {
4498            if (__len1 == 1)
4499            {   // __len1 >= __len2 && __len2 > 0, therefore __len2 == 1
4500                // It is known *__first > *__middle
4501                swap(*__first, *__middle);
4502                return;
4503            }
4504            // __len1 >= 2, __len2 >= 1
4505            __len11 = __len1 / 2;
4506            __m1 = __first;
4507            _VSTD::advance(__m1, __len11);
4508            __m2 = __lower_bound<_Compare>(__middle, __last, *__m1, __comp);
4509            __len21 = _VSTD::distance(__middle, __m2);
4510        }
4511        difference_type __len12 = __len1 - __len11;  // distance(__m1, __middle)
4512        difference_type __len22 = __len2 - __len21;  // distance(__m2, __last)
4513        // [__first, __m1) [__m1, __middle) [__middle, __m2) [__m2, __last)
4514        // swap middle two partitions
4515        __middle = _VSTD::rotate(__m1, __middle, __m2);
4516        // __len12 and __len21 now have swapped meanings
4517        // merge smaller range with recurisve call and larger with tail recursion elimination
4518        if (__len11 + __len21 < __len12 + __len22)
4519        {
4520            __inplace_merge<_Compare>(__first, __m1, __middle, __comp, __len11, __len21, __buff, __buff_size);
4521//          __inplace_merge<_Compare>(__middle, __m2, __last, __comp, __len12, __len22, __buff, __buff_size);
4522            __first = __middle;
4523            __middle = __m2;
4524            __len1 = __len12;
4525            __len2 = __len22;
4526        }
4527        else
4528        {
4529            __inplace_merge<_Compare>(__middle, __m2, __last, __comp, __len12, __len22, __buff, __buff_size);
4530//          __inplace_merge<_Compare>(__first, __m1, __middle, __comp, __len11, __len21, __buff, __buff_size);
4531            __last = __middle;
4532            __middle = __m1;
4533            __len1 = __len11;
4534            __len2 = __len21;
4535        }
4536    }
4537}
4538
4539template <class _BidirectionalIterator, class _Compare>
4540inline _LIBCPP_INLINE_VISIBILITY
4541void
4542inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
4543              _Compare __comp)
4544{
4545    typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
4546    typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
4547    difference_type __len1 = _VSTD::distance(__first, __middle);
4548    difference_type __len2 = _VSTD::distance(__middle, __last);
4549    difference_type __buf_size = _VSTD::min(__len1, __len2);
4550    pair<value_type*, ptrdiff_t> __buf = _VSTD::get_temporary_buffer<value_type>(__buf_size);
4551    unique_ptr<value_type, __return_temporary_buffer> __h(__buf.first);
4552
4553#ifdef _LIBCPP_DEBUG
4554    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
4555    __debug_less<_Compare> __c(__comp);
4556    return _VSTD::__inplace_merge<_Comp_ref>(__first, __middle, __last, __c, __len1, __len2,
4557                                            __buf.first, __buf.second);
4558#else  // _LIBCPP_DEBUG
4559    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4560    return _VSTD::__inplace_merge<_Comp_ref>(__first, __middle, __last, __comp, __len1, __len2,
4561                                            __buf.first, __buf.second);
4562#endif  // _LIBCPP_DEBUG
4563}
4564
4565template <class _BidirectionalIterator>
4566inline _LIBCPP_INLINE_VISIBILITY
4567void
4568inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last)
4569{
4570    _VSTD::inplace_merge(__first, __middle, __last,
4571                        __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
4572}
4573
4574// stable_sort
4575
4576template <class _Compare, class _InputIterator1, class _InputIterator2>
4577void
4578__merge_move_construct(_InputIterator1 __first1, _InputIterator1 __last1,
4579        _InputIterator2 __first2, _InputIterator2 __last2,
4580        typename iterator_traits<_InputIterator1>::value_type* __result, _Compare __comp)
4581{
4582    typedef typename iterator_traits<_InputIterator1>::value_type value_type;
4583    __destruct_n __d(0);
4584    unique_ptr<value_type, __destruct_n&> __h(__result, __d);
4585    for (; true; ++__result)
4586    {
4587        if (__first1 == __last1)
4588        {
4589            for (; __first2 != __last2; ++__first2, ++__result, __d.__incr((value_type*)0))
4590                ::new (__result) value_type(_VSTD::move(*__first2));
4591            __h.release();
4592            return;
4593        }
4594        if (__first2 == __last2)
4595        {
4596            for (; __first1 != __last1; ++__first1, ++__result, __d.__incr((value_type*)0))
4597                ::new (__result) value_type(_VSTD::move(*__first1));
4598            __h.release();
4599            return;
4600        }
4601        if (__comp(*__first2, *__first1))
4602        {
4603            ::new (__result) value_type(_VSTD::move(*__first2));
4604            __d.__incr((value_type*)0);
4605            ++__first2;
4606        }
4607        else
4608        {
4609            ::new (__result) value_type(_VSTD::move(*__first1));
4610            __d.__incr((value_type*)0);
4611            ++__first1;
4612        }
4613    }
4614}
4615
4616template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
4617void
4618__merge_move_assign(_InputIterator1 __first1, _InputIterator1 __last1,
4619        _InputIterator2 __first2, _InputIterator2 __last2,
4620        _OutputIterator __result, _Compare __comp)
4621{
4622    for (; __first1 != __last1; ++__result)
4623    {
4624        if (__first2 == __last2)
4625        {
4626            for (; __first1 != __last1; ++__first1, ++__result)
4627                *__result = _VSTD::move(*__first1);
4628            return;
4629        }
4630        if (__comp(*__first2, *__first1))
4631        {
4632            *__result = _VSTD::move(*__first2);
4633            ++__first2;
4634        }
4635        else
4636        {
4637            *__result = _VSTD::move(*__first1);
4638            ++__first1;
4639        }
4640    }
4641    for (; __first2 != __last2; ++__first2, ++__result)
4642        *__result = _VSTD::move(*__first2);
4643}
4644
4645template <class _Compare, class _RandomAccessIterator>
4646void
4647__stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
4648              typename iterator_traits<_RandomAccessIterator>::difference_type __len,
4649              typename iterator_traits<_RandomAccessIterator>::value_type* __buff, ptrdiff_t __buff_size);
4650
4651template <class _Compare, class _RandomAccessIterator>
4652void
4653__stable_sort_move(_RandomAccessIterator __first1, _RandomAccessIterator __last1, _Compare __comp,
4654                   typename iterator_traits<_RandomAccessIterator>::difference_type __len,
4655                   typename iterator_traits<_RandomAccessIterator>::value_type* __first2)
4656{
4657    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4658    switch (__len)
4659    {
4660    case 0:
4661        return;
4662    case 1:
4663        ::new(__first2) value_type(_VSTD::move(*__first1));
4664        return;
4665    case 2:
4666        __destruct_n __d(0);
4667        unique_ptr<value_type, __destruct_n&> __h2(__first2, __d);
4668        if (__comp(*--__last1, *__first1))
4669        {
4670            ::new(__first2) value_type(_VSTD::move(*__last1));
4671            __d.__incr((value_type*)0);
4672            ++__first2;
4673            ::new(__first2) value_type(_VSTD::move(*__first1));
4674        }
4675        else
4676        {
4677            ::new(__first2) value_type(_VSTD::move(*__first1));
4678            __d.__incr((value_type*)0);
4679            ++__first2;
4680            ::new(__first2) value_type(_VSTD::move(*__last1));
4681        }
4682        __h2.release();
4683        return;
4684    }
4685    if (__len <= 8)
4686    {
4687        __insertion_sort_move<_Compare>(__first1, __last1, __first2, __comp);
4688        return;
4689    }
4690    typename iterator_traits<_RandomAccessIterator>::difference_type __l2 = __len / 2;
4691    _RandomAccessIterator __m = __first1 + __l2;
4692    __stable_sort<_Compare>(__first1, __m, __comp, __l2, __first2, __l2);
4693    __stable_sort<_Compare>(__m, __last1, __comp, __len - __l2, __first2 + __l2, __len - __l2);
4694    __merge_move_construct<_Compare>(__first1, __m, __m, __last1, __first2, __comp);
4695}
4696
4697template <class _Tp>
4698struct __stable_sort_switch
4699{
4700    static const unsigned value = 128*is_trivially_copy_assignable<_Tp>::value;
4701};
4702
4703template <class _Compare, class _RandomAccessIterator>
4704void
4705__stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
4706              typename iterator_traits<_RandomAccessIterator>::difference_type __len,
4707              typename iterator_traits<_RandomAccessIterator>::value_type* __buff, ptrdiff_t __buff_size)
4708{
4709    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4710    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4711    switch (__len)
4712    {
4713    case 0:
4714    case 1:
4715        return;
4716    case 2:
4717        if (__comp(*--__last, *__first))
4718            swap(*__first, *__last);
4719        return;
4720    }
4721    if (__len <= static_cast<difference_type>(__stable_sort_switch<value_type>::value))
4722    {
4723        __insertion_sort<_Compare>(__first, __last, __comp);
4724        return;
4725    }
4726    typename iterator_traits<_RandomAccessIterator>::difference_type __l2 = __len / 2;
4727    _RandomAccessIterator __m = __first + __l2;
4728    if (__len <= __buff_size)
4729    {
4730        __destruct_n __d(0);
4731        unique_ptr<value_type, __destruct_n&> __h2(__buff, __d);
4732        __stable_sort_move<_Compare>(__first, __m, __comp, __l2, __buff);
4733        __d.__set(__l2, (value_type*)0);
4734        __stable_sort_move<_Compare>(__m, __last, __comp, __len - __l2, __buff + __l2);
4735        __d.__set(__len, (value_type*)0);
4736        __merge_move_assign<_Compare>(__buff, __buff + __l2, __buff + __l2, __buff + __len, __first, __comp);
4737//         __merge<_Compare>(move_iterator<value_type*>(__buff),
4738//                           move_iterator<value_type*>(__buff + __l2),
4739//                           move_iterator<_RandomAccessIterator>(__buff + __l2),
4740//                           move_iterator<_RandomAccessIterator>(__buff + __len),
4741//                           __first, __comp);
4742        return;
4743    }
4744    __stable_sort<_Compare>(__first, __m, __comp, __l2, __buff, __buff_size);
4745    __stable_sort<_Compare>(__m, __last, __comp, __len - __l2, __buff, __buff_size);
4746    __inplace_merge<_Compare>(__first, __m, __last, __comp, __l2, __len - __l2, __buff, __buff_size);
4747}
4748
4749template <class _RandomAccessIterator, class _Compare>
4750inline _LIBCPP_INLINE_VISIBILITY
4751void
4752stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4753{
4754    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4755    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4756    difference_type __len = __last - __first;
4757    pair<value_type*, ptrdiff_t> __buf(0, 0);
4758    unique_ptr<value_type, __return_temporary_buffer> __h;
4759    if (__len > static_cast<difference_type>(__stable_sort_switch<value_type>::value))
4760    {
4761        __buf = _VSTD::get_temporary_buffer<value_type>(__len);
4762        __h.reset(__buf.first);
4763    }
4764#ifdef _LIBCPP_DEBUG
4765    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
4766    __debug_less<_Compare> __c(__comp);
4767    __stable_sort<_Comp_ref>(__first, __last, __c, __len, __buf.first, __buf.second);
4768#else  // _LIBCPP_DEBUG
4769    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4770    __stable_sort<_Comp_ref>(__first, __last, __comp, __len, __buf.first, __buf.second);
4771#endif  // _LIBCPP_DEBUG
4772}
4773
4774template <class _RandomAccessIterator>
4775inline _LIBCPP_INLINE_VISIBILITY
4776void
4777stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last)
4778{
4779    _VSTD::stable_sort(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4780}
4781
4782// is_heap_until
4783
4784template <class _RandomAccessIterator, class _Compare>
4785_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _RandomAccessIterator
4786is_heap_until(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4787{
4788    typedef typename _VSTD::iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4789    difference_type __len = __last - __first;
4790    difference_type __p = 0;
4791    difference_type __c = 1;
4792    _RandomAccessIterator __pp = __first;
4793    while (__c < __len)
4794    {
4795        _RandomAccessIterator __cp = __first + __c;
4796        if (__comp(*__pp, *__cp))
4797            return __cp;
4798        ++__c;
4799        ++__cp;
4800        if (__c == __len)
4801            return __last;
4802        if (__comp(*__pp, *__cp))
4803            return __cp;
4804        ++__p;
4805        ++__pp;
4806        __c = 2 * __p + 1;
4807    }
4808    return __last;
4809}
4810
4811template<class _RandomAccessIterator>
4812_LIBCPP_NODISCARD_EXT inline
4813_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4814_RandomAccessIterator
4815is_heap_until(_RandomAccessIterator __first, _RandomAccessIterator __last)
4816{
4817    return _VSTD::is_heap_until(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4818}
4819
4820// is_heap
4821
4822template <class _RandomAccessIterator, class _Compare>
4823_LIBCPP_NODISCARD_EXT inline
4824_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4825bool
4826is_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4827{
4828    return _VSTD::is_heap_until(__first, __last, __comp) == __last;
4829}
4830
4831template<class _RandomAccessIterator>
4832_LIBCPP_NODISCARD_EXT inline
4833_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4834bool
4835is_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
4836{
4837    return _VSTD::is_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4838}
4839
4840// push_heap
4841
4842template <class _Compare, class _RandomAccessIterator>
4843void
4844__sift_up(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
4845          typename iterator_traits<_RandomAccessIterator>::difference_type __len)
4846{
4847    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4848    if (__len > 1)
4849    {
4850        __len = (__len - 2) / 2;
4851        _RandomAccessIterator __ptr = __first + __len;
4852        if (__comp(*__ptr, *--__last))
4853        {
4854            value_type __t(_VSTD::move(*__last));
4855            do
4856            {
4857                *__last = _VSTD::move(*__ptr);
4858                __last = __ptr;
4859                if (__len == 0)
4860                    break;
4861                __len = (__len - 1) / 2;
4862                __ptr = __first + __len;
4863            } while (__comp(*__ptr, __t));
4864            *__last = _VSTD::move(__t);
4865        }
4866    }
4867}
4868
4869template <class _RandomAccessIterator, class _Compare>
4870inline _LIBCPP_INLINE_VISIBILITY
4871void
4872push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4873{
4874#ifdef _LIBCPP_DEBUG
4875    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
4876    __debug_less<_Compare> __c(__comp);
4877    __sift_up<_Comp_ref>(__first, __last, __c, __last - __first);
4878#else  // _LIBCPP_DEBUG
4879    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4880    __sift_up<_Comp_ref>(__first, __last, __comp, __last - __first);
4881#endif  // _LIBCPP_DEBUG
4882}
4883
4884template <class _RandomAccessIterator>
4885inline _LIBCPP_INLINE_VISIBILITY
4886void
4887push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
4888{
4889    _VSTD::push_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4890}
4891
4892// pop_heap
4893
4894template <class _Compare, class _RandomAccessIterator>
4895void
4896__sift_down(_RandomAccessIterator __first, _RandomAccessIterator /*__last*/,
4897            _Compare __comp,
4898            typename iterator_traits<_RandomAccessIterator>::difference_type __len,
4899            _RandomAccessIterator __start)
4900{
4901    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4902    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4903    // left-child of __start is at 2 * __start + 1
4904    // right-child of __start is at 2 * __start + 2
4905    difference_type __child = __start - __first;
4906
4907    if (__len < 2 || (__len - 2) / 2 < __child)
4908        return;
4909
4910    __child = 2 * __child + 1;
4911    _RandomAccessIterator __child_i = __first + __child;
4912
4913    if ((__child + 1) < __len && __comp(*__child_i, *(__child_i + 1))) {
4914        // right-child exists and is greater than left-child
4915        ++__child_i;
4916        ++__child;
4917    }
4918
4919    // check if we are in heap-order
4920    if (__comp(*__child_i, *__start))
4921        // we are, __start is larger than it's largest child
4922        return;
4923
4924    value_type __top(_VSTD::move(*__start));
4925    do
4926    {
4927        // we are not in heap-order, swap the parent with it's largest child
4928        *__start = _VSTD::move(*__child_i);
4929        __start = __child_i;
4930
4931        if ((__len - 2) / 2 < __child)
4932            break;
4933
4934        // recompute the child based off of the updated parent
4935        __child = 2 * __child + 1;
4936        __child_i = __first + __child;
4937
4938        if ((__child + 1) < __len && __comp(*__child_i, *(__child_i + 1))) {
4939            // right-child exists and is greater than left-child
4940            ++__child_i;
4941            ++__child;
4942        }
4943
4944        // check if we are in heap-order
4945    } while (!__comp(*__child_i, __top));
4946    *__start = _VSTD::move(__top);
4947}
4948
4949template <class _Compare, class _RandomAccessIterator>
4950inline _LIBCPP_INLINE_VISIBILITY
4951void
4952__pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
4953           typename iterator_traits<_RandomAccessIterator>::difference_type __len)
4954{
4955    if (__len > 1)
4956    {
4957        swap(*__first, *--__last);
4958        __sift_down<_Compare>(__first, __last, __comp, __len - 1, __first);
4959    }
4960}
4961
4962template <class _RandomAccessIterator, class _Compare>
4963inline _LIBCPP_INLINE_VISIBILITY
4964void
4965pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4966{
4967#ifdef _LIBCPP_DEBUG
4968    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
4969    __debug_less<_Compare> __c(__comp);
4970    __pop_heap<_Comp_ref>(__first, __last, __c, __last - __first);
4971#else  // _LIBCPP_DEBUG
4972    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4973    __pop_heap<_Comp_ref>(__first, __last, __comp, __last - __first);
4974#endif  // _LIBCPP_DEBUG
4975}
4976
4977template <class _RandomAccessIterator>
4978inline _LIBCPP_INLINE_VISIBILITY
4979void
4980pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
4981{
4982    _VSTD::pop_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4983}
4984
4985// make_heap
4986
4987template <class _Compare, class _RandomAccessIterator>
4988void
4989__make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4990{
4991    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4992    difference_type __n = __last - __first;
4993    if (__n > 1)
4994    {
4995        // start from the first parent, there is no need to consider children
4996        for (difference_type __start = (__n - 2) / 2; __start >= 0; --__start)
4997        {
4998            __sift_down<_Compare>(__first, __last, __comp, __n, __first + __start);
4999        }
5000    }
5001}
5002
5003template <class _RandomAccessIterator, class _Compare>
5004inline _LIBCPP_INLINE_VISIBILITY
5005void
5006make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
5007{
5008#ifdef _LIBCPP_DEBUG
5009    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5010    __debug_less<_Compare> __c(__comp);
5011    __make_heap<_Comp_ref>(__first, __last, __c);
5012#else  // _LIBCPP_DEBUG
5013    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5014    __make_heap<_Comp_ref>(__first, __last, __comp);
5015#endif  // _LIBCPP_DEBUG
5016}
5017
5018template <class _RandomAccessIterator>
5019inline _LIBCPP_INLINE_VISIBILITY
5020void
5021make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
5022{
5023    _VSTD::make_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5024}
5025
5026// sort_heap
5027
5028template <class _Compare, class _RandomAccessIterator>
5029void
5030__sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
5031{
5032    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
5033    for (difference_type __n = __last - __first; __n > 1; --__last, --__n)
5034        __pop_heap<_Compare>(__first, __last, __comp, __n);
5035}
5036
5037template <class _RandomAccessIterator, class _Compare>
5038inline _LIBCPP_INLINE_VISIBILITY
5039void
5040sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
5041{
5042#ifdef _LIBCPP_DEBUG
5043    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5044    __debug_less<_Compare> __c(__comp);
5045    __sort_heap<_Comp_ref>(__first, __last, __c);
5046#else  // _LIBCPP_DEBUG
5047    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5048    __sort_heap<_Comp_ref>(__first, __last, __comp);
5049#endif  // _LIBCPP_DEBUG
5050}
5051
5052template <class _RandomAccessIterator>
5053inline _LIBCPP_INLINE_VISIBILITY
5054void
5055sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
5056{
5057    _VSTD::sort_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5058}
5059
5060// partial_sort
5061
5062template <class _Compare, class _RandomAccessIterator>
5063void
5064__partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last,
5065             _Compare __comp)
5066{
5067    __make_heap<_Compare>(__first, __middle, __comp);
5068    typename iterator_traits<_RandomAccessIterator>::difference_type __len = __middle - __first;
5069    for (_RandomAccessIterator __i = __middle; __i != __last; ++__i)
5070    {
5071        if (__comp(*__i, *__first))
5072        {
5073            swap(*__i, *__first);
5074            __sift_down<_Compare>(__first, __middle, __comp, __len, __first);
5075        }
5076    }
5077    __sort_heap<_Compare>(__first, __middle, __comp);
5078}
5079
5080template <class _RandomAccessIterator, class _Compare>
5081inline _LIBCPP_INLINE_VISIBILITY
5082void
5083partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last,
5084             _Compare __comp)
5085{
5086#ifdef _LIBCPP_DEBUG
5087    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5088    __debug_less<_Compare> __c(__comp);
5089    __partial_sort<_Comp_ref>(__first, __middle, __last, __c);
5090#else  // _LIBCPP_DEBUG
5091    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5092    __partial_sort<_Comp_ref>(__first, __middle, __last, __comp);
5093#endif  // _LIBCPP_DEBUG
5094}
5095
5096template <class _RandomAccessIterator>
5097inline _LIBCPP_INLINE_VISIBILITY
5098void
5099partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last)
5100{
5101    _VSTD::partial_sort(__first, __middle, __last,
5102                       __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5103}
5104
5105// partial_sort_copy
5106
5107template <class _Compare, class _InputIterator, class _RandomAccessIterator>
5108_RandomAccessIterator
5109__partial_sort_copy(_InputIterator __first, _InputIterator __last,
5110                    _RandomAccessIterator __result_first, _RandomAccessIterator __result_last, _Compare __comp)
5111{
5112    _RandomAccessIterator __r = __result_first;
5113    if (__r != __result_last)
5114    {
5115        for (; __first != __last && __r != __result_last; (void) ++__first, ++__r)
5116            *__r = *__first;
5117        __make_heap<_Compare>(__result_first, __r, __comp);
5118        typename iterator_traits<_RandomAccessIterator>::difference_type __len = __r - __result_first;
5119        for (; __first != __last; ++__first)
5120            if (__comp(*__first, *__result_first))
5121            {
5122                *__result_first = *__first;
5123                __sift_down<_Compare>(__result_first, __r, __comp, __len, __result_first);
5124            }
5125        __sort_heap<_Compare>(__result_first, __r, __comp);
5126    }
5127    return __r;
5128}
5129
5130template <class _InputIterator, class _RandomAccessIterator, class _Compare>
5131inline _LIBCPP_INLINE_VISIBILITY
5132_RandomAccessIterator
5133partial_sort_copy(_InputIterator __first, _InputIterator __last,
5134                  _RandomAccessIterator __result_first, _RandomAccessIterator __result_last, _Compare __comp)
5135{
5136#ifdef _LIBCPP_DEBUG
5137    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5138    __debug_less<_Compare> __c(__comp);
5139    return __partial_sort_copy<_Comp_ref>(__first, __last, __result_first, __result_last, __c);
5140#else  // _LIBCPP_DEBUG
5141    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5142    return __partial_sort_copy<_Comp_ref>(__first, __last, __result_first, __result_last, __comp);
5143#endif  // _LIBCPP_DEBUG
5144}
5145
5146template <class _InputIterator, class _RandomAccessIterator>
5147inline _LIBCPP_INLINE_VISIBILITY
5148_RandomAccessIterator
5149partial_sort_copy(_InputIterator __first, _InputIterator __last,
5150                  _RandomAccessIterator __result_first, _RandomAccessIterator __result_last)
5151{
5152    return _VSTD::partial_sort_copy(__first, __last, __result_first, __result_last,
5153                                   __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5154}
5155
5156// nth_element
5157
5158template <class _Compare, class _RandomAccessIterator>
5159void
5160__nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth, _RandomAccessIterator __last, _Compare __comp)
5161{
5162    // _Compare is known to be a reference type
5163    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
5164    const difference_type __limit = 7;
5165    while (true)
5166    {
5167    __restart:
5168        if (__nth == __last)
5169            return;
5170        difference_type __len = __last - __first;
5171        switch (__len)
5172        {
5173        case 0:
5174        case 1:
5175            return;
5176        case 2:
5177            if (__comp(*--__last, *__first))
5178                swap(*__first, *__last);
5179            return;
5180        case 3:
5181            {
5182            _RandomAccessIterator __m = __first;
5183            _VSTD::__sort3<_Compare>(__first, ++__m, --__last, __comp);
5184            return;
5185            }
5186        }
5187        if (__len <= __limit)
5188        {
5189            __selection_sort<_Compare>(__first, __last, __comp);
5190            return;
5191        }
5192        // __len > __limit >= 3
5193        _RandomAccessIterator __m = __first + __len/2;
5194        _RandomAccessIterator __lm1 = __last;
5195        unsigned __n_swaps = _VSTD::__sort3<_Compare>(__first, __m, --__lm1, __comp);
5196        // *__m is median
5197        // partition [__first, __m) < *__m and *__m <= [__m, __last)
5198        // (this inhibits tossing elements equivalent to __m around unnecessarily)
5199        _RandomAccessIterator __i = __first;
5200        _RandomAccessIterator __j = __lm1;
5201        // j points beyond range to be tested, *__lm1 is known to be <= *__m
5202        // The search going up is known to be guarded but the search coming down isn't.
5203        // Prime the downward search with a guard.
5204        if (!__comp(*__i, *__m))  // if *__first == *__m
5205        {
5206            // *__first == *__m, *__first doesn't go in first part
5207            // manually guard downward moving __j against __i
5208            while (true)
5209            {
5210                if (__i == --__j)
5211                {
5212                    // *__first == *__m, *__m <= all other elements
5213                    // Parition instead into [__first, __i) == *__first and *__first < [__i, __last)
5214                    ++__i;  // __first + 1
5215                    __j = __last;
5216                    if (!__comp(*__first, *--__j))  // we need a guard if *__first == *(__last-1)
5217                    {
5218                        while (true)
5219                        {
5220                            if (__i == __j)
5221                                return;  // [__first, __last) all equivalent elements
5222                            if (__comp(*__first, *__i))
5223                            {
5224                                swap(*__i, *__j);
5225                                ++__n_swaps;
5226                                ++__i;
5227                                break;
5228                            }
5229                            ++__i;
5230                        }
5231                    }
5232                    // [__first, __i) == *__first and *__first < [__j, __last) and __j == __last - 1
5233                    if (__i == __j)
5234                        return;
5235                    while (true)
5236                    {
5237                        while (!__comp(*__first, *__i))
5238                            ++__i;
5239                        while (__comp(*__first, *--__j))
5240                            ;
5241                        if (__i >= __j)
5242                            break;
5243                        swap(*__i, *__j);
5244                        ++__n_swaps;
5245                        ++__i;
5246                    }
5247                    // [__first, __i) == *__first and *__first < [__i, __last)
5248                    // The first part is sorted,
5249                    if (__nth < __i)
5250                        return;
5251                    // __nth_element the secod part
5252                    // __nth_element<_Compare>(__i, __nth, __last, __comp);
5253                    __first = __i;
5254                    goto __restart;
5255                }
5256                if (__comp(*__j, *__m))
5257                {
5258                    swap(*__i, *__j);
5259                    ++__n_swaps;
5260                    break;  // found guard for downward moving __j, now use unguarded partition
5261                }
5262            }
5263        }
5264        ++__i;
5265        // j points beyond range to be tested, *__lm1 is known to be <= *__m
5266        // if not yet partitioned...
5267        if (__i < __j)
5268        {
5269            // known that *(__i - 1) < *__m
5270            while (true)
5271            {
5272                // __m still guards upward moving __i
5273                while (__comp(*__i, *__m))
5274                    ++__i;
5275                // It is now known that a guard exists for downward moving __j
5276                while (!__comp(*--__j, *__m))
5277                    ;
5278                if (__i >= __j)
5279                    break;
5280                swap(*__i, *__j);
5281                ++__n_swaps;
5282                // It is known that __m != __j
5283                // If __m just moved, follow it
5284                if (__m == __i)
5285                    __m = __j;
5286                ++__i;
5287            }
5288        }
5289        // [__first, __i) < *__m and *__m <= [__i, __last)
5290        if (__i != __m && __comp(*__m, *__i))
5291        {
5292            swap(*__i, *__m);
5293            ++__n_swaps;
5294        }
5295        // [__first, __i) < *__i and *__i <= [__i+1, __last)
5296        if (__nth == __i)
5297            return;
5298        if (__n_swaps == 0)
5299        {
5300            // We were given a perfectly partitioned sequence.  Coincidence?
5301            if (__nth < __i)
5302            {
5303                // Check for [__first, __i) already sorted
5304                __j = __m = __first;
5305                while (++__j != __i)
5306                {
5307                    if (__comp(*__j, *__m))
5308                        // not yet sorted, so sort
5309                        goto not_sorted;
5310                    __m = __j;
5311                }
5312                // [__first, __i) sorted
5313                return;
5314            }
5315            else
5316            {
5317                // Check for [__i, __last) already sorted
5318                __j = __m = __i;
5319                while (++__j != __last)
5320                {
5321                    if (__comp(*__j, *__m))
5322                        // not yet sorted, so sort
5323                        goto not_sorted;
5324                    __m = __j;
5325                }
5326                // [__i, __last) sorted
5327                return;
5328            }
5329        }
5330not_sorted:
5331        // __nth_element on range containing __nth
5332        if (__nth < __i)
5333        {
5334            // __nth_element<_Compare>(__first, __nth, __i, __comp);
5335            __last = __i;
5336        }
5337        else
5338        {
5339            // __nth_element<_Compare>(__i+1, __nth, __last, __comp);
5340            __first = ++__i;
5341        }
5342    }
5343}
5344
5345template <class _RandomAccessIterator, class _Compare>
5346inline _LIBCPP_INLINE_VISIBILITY
5347void
5348nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth, _RandomAccessIterator __last, _Compare __comp)
5349{
5350#ifdef _LIBCPP_DEBUG
5351    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5352    __debug_less<_Compare> __c(__comp);
5353    __nth_element<_Comp_ref>(__first, __nth, __last, __c);
5354#else  // _LIBCPP_DEBUG
5355    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5356    __nth_element<_Comp_ref>(__first, __nth, __last, __comp);
5357#endif  // _LIBCPP_DEBUG
5358}
5359
5360template <class _RandomAccessIterator>
5361inline _LIBCPP_INLINE_VISIBILITY
5362void
5363nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth, _RandomAccessIterator __last)
5364{
5365    _VSTD::nth_element(__first, __nth, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5366}
5367
5368// includes
5369
5370template <class _Compare, class _InputIterator1, class _InputIterator2>
5371_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
5372__includes(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2,
5373           _Compare __comp)
5374{
5375    for (; __first2 != __last2; ++__first1)
5376    {
5377        if (__first1 == __last1 || __comp(*__first2, *__first1))
5378            return false;
5379        if (!__comp(*__first1, *__first2))
5380            ++__first2;
5381    }
5382    return true;
5383}
5384
5385template <class _InputIterator1, class _InputIterator2, class _Compare>
5386_LIBCPP_NODISCARD_EXT inline
5387_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5388bool
5389includes(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2,
5390         _Compare __comp)
5391{
5392#ifdef _LIBCPP_DEBUG
5393    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5394    __debug_less<_Compare> __c(__comp);
5395    return __includes<_Comp_ref>(__first1, __last1, __first2, __last2, __c);
5396#else  // _LIBCPP_DEBUG
5397    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5398    return __includes<_Comp_ref>(__first1, __last1, __first2, __last2, __comp);
5399#endif  // _LIBCPP_DEBUG
5400}
5401
5402template <class _InputIterator1, class _InputIterator2>
5403_LIBCPP_NODISCARD_EXT inline
5404_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5405bool
5406includes(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2)
5407{
5408    return _VSTD::includes(__first1, __last1, __first2, __last2,
5409                          __less<typename iterator_traits<_InputIterator1>::value_type,
5410                                 typename iterator_traits<_InputIterator2>::value_type>());
5411}
5412
5413// set_union
5414
5415template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
5416_OutputIterator
5417__set_union(_InputIterator1 __first1, _InputIterator1 __last1,
5418            _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5419{
5420    for (; __first1 != __last1; ++__result)
5421    {
5422        if (__first2 == __last2)
5423            return _VSTD::copy(__first1, __last1, __result);
5424        if (__comp(*__first2, *__first1))
5425        {
5426            *__result = *__first2;
5427            ++__first2;
5428        }
5429        else
5430        {
5431            if (!__comp(*__first1, *__first2))
5432                ++__first2;
5433            *__result = *__first1;
5434            ++__first1;
5435        }
5436    }
5437    return _VSTD::copy(__first2, __last2, __result);
5438}
5439
5440template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
5441inline _LIBCPP_INLINE_VISIBILITY
5442_OutputIterator
5443set_union(_InputIterator1 __first1, _InputIterator1 __last1,
5444          _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5445{
5446#ifdef _LIBCPP_DEBUG
5447    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5448    __debug_less<_Compare> __c(__comp);
5449    return __set_union<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __c);
5450#else  // _LIBCPP_DEBUG
5451    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5452    return __set_union<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
5453#endif  // _LIBCPP_DEBUG
5454}
5455
5456template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
5457inline _LIBCPP_INLINE_VISIBILITY
5458_OutputIterator
5459set_union(_InputIterator1 __first1, _InputIterator1 __last1,
5460          _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
5461{
5462    return _VSTD::set_union(__first1, __last1, __first2, __last2, __result,
5463                          __less<typename iterator_traits<_InputIterator1>::value_type,
5464                                 typename iterator_traits<_InputIterator2>::value_type>());
5465}
5466
5467// set_intersection
5468
5469template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
5470_LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator
5471__set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
5472                   _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5473{
5474    while (__first1 != __last1 && __first2 != __last2)
5475    {
5476        if (__comp(*__first1, *__first2))
5477            ++__first1;
5478        else
5479        {
5480            if (!__comp(*__first2, *__first1))
5481            {
5482                *__result = *__first1;
5483                ++__result;
5484                ++__first1;
5485            }
5486            ++__first2;
5487        }
5488    }
5489    return __result;
5490}
5491
5492template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
5493inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5494_OutputIterator
5495set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
5496                 _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5497{
5498#ifdef _LIBCPP_DEBUG
5499    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5500    __debug_less<_Compare> __c(__comp);
5501    return __set_intersection<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __c);
5502#else  // _LIBCPP_DEBUG
5503    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5504    return __set_intersection<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
5505#endif  // _LIBCPP_DEBUG
5506}
5507
5508template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
5509inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5510_OutputIterator
5511set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
5512                 _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
5513{
5514    return _VSTD::set_intersection(__first1, __last1, __first2, __last2, __result,
5515                                  __less<typename iterator_traits<_InputIterator1>::value_type,
5516                                         typename iterator_traits<_InputIterator2>::value_type>());
5517}
5518
5519// set_difference
5520
5521template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
5522_OutputIterator
5523__set_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5524                 _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5525{
5526    while (__first1 != __last1)
5527    {
5528        if (__first2 == __last2)
5529            return _VSTD::copy(__first1, __last1, __result);
5530        if (__comp(*__first1, *__first2))
5531        {
5532            *__result = *__first1;
5533            ++__result;
5534            ++__first1;
5535        }
5536        else
5537        {
5538            if (!__comp(*__first2, *__first1))
5539                ++__first1;
5540            ++__first2;
5541        }
5542    }
5543    return __result;
5544}
5545
5546template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
5547inline _LIBCPP_INLINE_VISIBILITY
5548_OutputIterator
5549set_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5550               _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5551{
5552#ifdef _LIBCPP_DEBUG
5553    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5554    __debug_less<_Compare> __c(__comp);
5555    return __set_difference<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __c);
5556#else  // _LIBCPP_DEBUG
5557    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5558    return __set_difference<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
5559#endif  // _LIBCPP_DEBUG
5560}
5561
5562template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
5563inline _LIBCPP_INLINE_VISIBILITY
5564_OutputIterator
5565set_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5566               _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
5567{
5568    return _VSTD::set_difference(__first1, __last1, __first2, __last2, __result,
5569                                __less<typename iterator_traits<_InputIterator1>::value_type,
5570                                       typename iterator_traits<_InputIterator2>::value_type>());
5571}
5572
5573// set_symmetric_difference
5574
5575template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
5576_OutputIterator
5577__set_symmetric_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5578                           _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5579{
5580    while (__first1 != __last1)
5581    {
5582        if (__first2 == __last2)
5583            return _VSTD::copy(__first1, __last1, __result);
5584        if (__comp(*__first1, *__first2))
5585        {
5586            *__result = *__first1;
5587            ++__result;
5588            ++__first1;
5589        }
5590        else
5591        {
5592            if (__comp(*__first2, *__first1))
5593            {
5594                *__result = *__first2;
5595                ++__result;
5596            }
5597            else
5598                ++__first1;
5599            ++__first2;
5600        }
5601    }
5602    return _VSTD::copy(__first2, __last2, __result);
5603}
5604
5605template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
5606inline _LIBCPP_INLINE_VISIBILITY
5607_OutputIterator
5608set_symmetric_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5609                         _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5610{
5611#ifdef _LIBCPP_DEBUG
5612    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5613    __debug_less<_Compare> __c(__comp);
5614    return __set_symmetric_difference<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __c);
5615#else  // _LIBCPP_DEBUG
5616    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5617    return __set_symmetric_difference<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
5618#endif  // _LIBCPP_DEBUG
5619}
5620
5621template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
5622inline _LIBCPP_INLINE_VISIBILITY
5623_OutputIterator
5624set_symmetric_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5625                         _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
5626{
5627    return _VSTD::set_symmetric_difference(__first1, __last1, __first2, __last2, __result,
5628                                          __less<typename iterator_traits<_InputIterator1>::value_type,
5629                                                 typename iterator_traits<_InputIterator2>::value_type>());
5630}
5631
5632// lexicographical_compare
5633
5634template <class _Compare, class _InputIterator1, class _InputIterator2>
5635_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
5636__lexicographical_compare(_InputIterator1 __first1, _InputIterator1 __last1,
5637                          _InputIterator2 __first2, _InputIterator2 __last2, _Compare __comp)
5638{
5639    for (; __first2 != __last2; ++__first1, (void) ++__first2)
5640    {
5641        if (__first1 == __last1 || __comp(*__first1, *__first2))
5642            return true;
5643        if (__comp(*__first2, *__first1))
5644            return false;
5645    }
5646    return false;
5647}
5648
5649template <class _InputIterator1, class _InputIterator2, class _Compare>
5650_LIBCPP_NODISCARD_EXT inline
5651_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5652bool
5653lexicographical_compare(_InputIterator1 __first1, _InputIterator1 __last1,
5654                        _InputIterator2 __first2, _InputIterator2 __last2, _Compare __comp)
5655{
5656#ifdef _LIBCPP_DEBUG
5657    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5658    __debug_less<_Compare> __c(__comp);
5659    return __lexicographical_compare<_Comp_ref>(__first1, __last1, __first2, __last2, __c);
5660#else  // _LIBCPP_DEBUG
5661    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5662    return __lexicographical_compare<_Comp_ref>(__first1, __last1, __first2, __last2, __comp);
5663#endif  // _LIBCPP_DEBUG
5664}
5665
5666template <class _InputIterator1, class _InputIterator2>
5667_LIBCPP_NODISCARD_EXT inline
5668_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5669bool
5670lexicographical_compare(_InputIterator1 __first1, _InputIterator1 __last1,
5671                        _InputIterator2 __first2, _InputIterator2 __last2)
5672{
5673    return _VSTD::lexicographical_compare(__first1, __last1, __first2, __last2,
5674                                         __less<typename iterator_traits<_InputIterator1>::value_type,
5675                                                typename iterator_traits<_InputIterator2>::value_type>());
5676}
5677
5678// next_permutation
5679
5680template <class _Compare, class _BidirectionalIterator>
5681bool
5682__next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp)
5683{
5684    _BidirectionalIterator __i = __last;
5685    if (__first == __last || __first == --__i)
5686        return false;
5687    while (true)
5688    {
5689        _BidirectionalIterator __ip1 = __i;
5690        if (__comp(*--__i, *__ip1))
5691        {
5692            _BidirectionalIterator __j = __last;
5693            while (!__comp(*__i, *--__j))
5694                ;
5695            swap(*__i, *__j);
5696            _VSTD::reverse(__ip1, __last);
5697            return true;
5698        }
5699        if (__i == __first)
5700        {
5701            _VSTD::reverse(__first, __last);
5702            return false;
5703        }
5704    }
5705}
5706
5707template <class _BidirectionalIterator, class _Compare>
5708inline _LIBCPP_INLINE_VISIBILITY
5709bool
5710next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp)
5711{
5712#ifdef _LIBCPP_DEBUG
5713    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5714    __debug_less<_Compare> __c(__comp);
5715    return __next_permutation<_Comp_ref>(__first, __last, __c);
5716#else  // _LIBCPP_DEBUG
5717    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5718    return __next_permutation<_Comp_ref>(__first, __last, __comp);
5719#endif  // _LIBCPP_DEBUG
5720}
5721
5722template <class _BidirectionalIterator>
5723inline _LIBCPP_INLINE_VISIBILITY
5724bool
5725next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last)
5726{
5727    return _VSTD::next_permutation(__first, __last,
5728                                  __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
5729}
5730
5731// prev_permutation
5732
5733template <class _Compare, class _BidirectionalIterator>
5734bool
5735__prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp)
5736{
5737    _BidirectionalIterator __i = __last;
5738    if (__first == __last || __first == --__i)
5739        return false;
5740    while (true)
5741    {
5742        _BidirectionalIterator __ip1 = __i;
5743        if (__comp(*__ip1, *--__i))
5744        {
5745            _BidirectionalIterator __j = __last;
5746            while (!__comp(*--__j, *__i))
5747                ;
5748            swap(*__i, *__j);
5749            _VSTD::reverse(__ip1, __last);
5750            return true;
5751        }
5752        if (__i == __first)
5753        {
5754            _VSTD::reverse(__first, __last);
5755            return false;
5756        }
5757    }
5758}
5759
5760template <class _BidirectionalIterator, class _Compare>
5761inline _LIBCPP_INLINE_VISIBILITY
5762bool
5763prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp)
5764{
5765#ifdef _LIBCPP_DEBUG
5766    typedef typename add_lvalue_reference<__debug_less<_Compare> >::type _Comp_ref;
5767    __debug_less<_Compare> __c(__comp);
5768    return __prev_permutation<_Comp_ref>(__first, __last, __c);
5769#else  // _LIBCPP_DEBUG
5770    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
5771    return __prev_permutation<_Comp_ref>(__first, __last, __comp);
5772#endif  // _LIBCPP_DEBUG
5773}
5774
5775template <class _BidirectionalIterator>
5776inline _LIBCPP_INLINE_VISIBILITY
5777bool
5778prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last)
5779{
5780    return _VSTD::prev_permutation(__first, __last,
5781                                  __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
5782}
5783
5784_LIBCPP_END_NAMESPACE_STD
5785
5786_LIBCPP_POP_MACROS
5787
5788#endif  // _LIBCPP_ALGORITHM
5789