1// Queue implementation -*- C++ -*-
2
3// Copyright (C) 2001-2025 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/*
26 *
27 * Copyright (c) 1994
28 * Hewlett-Packard Company
29 *
30 * Permission to use, copy, modify, distribute and sell this software
31 * and its documentation for any purpose is hereby granted without fee,
32 * provided that the above copyright notice appear in all copies and
33 * that both that copyright notice and this permission notice appear
34 * in supporting documentation. Hewlett-Packard Company makes no
35 * representations about the suitability of this software for any
36 * purpose. It is provided "as is" without express or implied warranty.
37 *
38 *
39 * Copyright (c) 1996,1997
40 * Silicon Graphics Computer Systems, Inc.
41 *
42 * Permission to use, copy, modify, distribute and sell this software
43 * and its documentation for any purpose is hereby granted without fee,
44 * provided that the above copyright notice appear in all copies and
45 * that both that copyright notice and this permission notice appear
46 * in supporting documentation. Silicon Graphics makes no
47 * representations about the suitability of this software for any
48 * purpose. It is provided "as is" without express or implied warranty.
49 */
50
51/** @file bits/stl_queue.h
52 * This is an internal header file, included by other library headers.
53 * Do not attempt to use it directly. @headername{queue}
54 */
55
56#ifndef _STL_QUEUE_H
57#define _STL_QUEUE_H 1
58
59#include <bits/concept_check.h>
60#include <debug/debug.h>
61#if __cplusplus >= 201103L
62# include <bits/uses_allocator.h>
63#endif
64#if __glibcxx_containers_ranges // C++ >= 23
65# include <ranges> // ranges::to
66# include <bits/ranges_algobase.h> // ranges::copy
67#endif
68
69namespace std _GLIBCXX_VISIBILITY(default)
70{
71_GLIBCXX_BEGIN_NAMESPACE_VERSION
72
73#if __glibcxx_format_ranges
74 template<typename, typename> class formatter;
75#endif
76
77 /**
78 * @brief A standard container giving FIFO behavior.
79 *
80 * @ingroup sequences
81 *
82 * @tparam _Tp Type of element.
83 * @tparam _Sequence Type of underlying sequence, defaults to deque<_Tp>.
84 *
85 * Meets many of the requirements of a
86 * <a href="tables.html#65">container</a>,
87 * but does not define anything to do with iterators. Very few of the
88 * other standard container interfaces are defined.
89 *
90 * This is not a true container, but an @e adaptor. It holds another
91 * container, and provides a wrapper interface to that container. The
92 * wrapper is what enforces strict first-in-first-out %queue behavior.
93 *
94 * The second template parameter defines the type of the underlying
95 * sequence/container. It defaults to std::deque, but it can be any type
96 * that supports @c front, @c back, @c push_back, and @c pop_front,
97 * such as std::list or an appropriate user-defined type.
98 *
99 * Members not found in @a normal containers are @c container_type,
100 * which is a typedef for the second Sequence parameter, and @c push and
101 * @c pop, which are standard %queue/FIFO operations.
102 */
103 template<typename _Tp, typename _Sequence = deque<_Tp> >
104 class queue
105 {
106#ifdef _GLIBCXX_CONCEPT_CHECKS
107 // concept requirements
108 typedef typename _Sequence::value_type _Sequence_value_type;
109# if __cplusplus < 201103L
110 __glibcxx_class_requires(_Tp, _SGIAssignableConcept)
111# endif
112 __glibcxx_class_requires(_Sequence, _FrontInsertionSequenceConcept)
113 __glibcxx_class_requires(_Sequence, _BackInsertionSequenceConcept)
114 __glibcxx_class_requires2(_Tp, _Sequence_value_type, _SameTypeConcept)
115#endif
116
117 template<typename _Tp1, typename _Seq1>
118 friend bool
119 operator==(const queue<_Tp1, _Seq1>&, const queue<_Tp1, _Seq1>&);
120
121 template<typename _Tp1, typename _Seq1>
122 friend bool
123 operator<(const queue<_Tp1, _Seq1>&, const queue<_Tp1, _Seq1>&);
124
125#if __cpp_lib_three_way_comparison
126 template<typename _Tp1, three_way_comparable _Seq1>
127 friend compare_three_way_result_t<_Seq1>
128 operator<=>(const queue<_Tp1, _Seq1>&, const queue<_Tp1, _Seq1>&);
129#endif
130
131#if __cplusplus >= 201103L
132 template<typename _Alloc>
133 using _Uses = typename
134 enable_if<uses_allocator<_Sequence, _Alloc>::value>::type;
135
136#if __cplusplus >= 201703L
137 // _GLIBCXX_RESOLVE_LIB_DEFECTS
138 // 2566. Requirements on the first template parameter of container
139 // adaptors
140 static_assert(is_same<_Tp, typename _Sequence::value_type>::value,
141 "value_type must be the same as the underlying container");
142#endif // C++17
143#endif // C++11
144
145 public:
146 typedef typename _Sequence::value_type value_type;
147 typedef typename _Sequence::reference reference;
148 typedef typename _Sequence::const_reference const_reference;
149 typedef typename _Sequence::size_type size_type;
150 typedef _Sequence container_type;
151
152 protected:
153 /* Maintainers wondering why this isn't uglified as per style
154 * guidelines should note that this name is specified in the standard,
155 * C++98 [23.2.3.1].
156 * (Why? Presumably for the same reason that it's protected instead
157 * of private: to allow derivation. But none of the other
158 * containers allow for derivation. Odd.)
159 */
160 /// @c c is the underlying container.
161 _Sequence c;
162
163 public:
164 /**
165 * @brief Default constructor creates no elements.
166 */
167#if __cplusplus < 201103L
168 explicit
169 queue(const _Sequence& __c = _Sequence())
170 : c(__c) { }
171#else
172 template<typename _Seq = _Sequence, typename _Requires = typename
173 enable_if<is_default_constructible<_Seq>::value>::type>
174 queue()
175 : c() { }
176
177 explicit
178 queue(const _Sequence& __c)
179 : c(__c) { }
180
181 explicit
182 queue(_Sequence&& __c)
183 : c(std::move(__c)) { }
184
185 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
186 explicit
187 queue(const _Alloc& __a)
188 : c(__a) { }
189
190 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
191 queue(const _Sequence& __c, const _Alloc& __a)
192 : c(__c, __a) { }
193
194 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
195 queue(_Sequence&& __c, const _Alloc& __a)
196 : c(std::move(__c), __a) { }
197
198 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
199 queue(const queue& __q, const _Alloc& __a)
200 : c(__q.c, __a) { }
201
202 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
203 queue(queue&& __q, const _Alloc& __a)
204 : c(std::move(__q.c), __a) { }
205#endif
206
207#ifdef __glibcxx_adaptor_iterator_pair_constructor // C++ >= 23 && HOSTED
208 template<typename _InputIterator,
209 typename = _RequireInputIter<_InputIterator>>
210 queue(_InputIterator __first, _InputIterator __last)
211 : c(__first, __last) { }
212
213 template<typename _InputIterator, typename _Alloc,
214 typename = _RequireInputIter<_InputIterator>,
215 typename = _Uses<_Alloc>>
216 queue(_InputIterator __first, _InputIterator __last, const _Alloc& __a)
217 : c(__first, __last, __a) { }
218#endif
219
220#if __glibcxx_containers_ranges // C++ >= 23
221 /**
222 * @brief Construct a queue from a range.
223 * @since C++23
224 */
225 template<__detail::__container_compatible_range<_Tp> _Rg>
226 queue(from_range_t, _Rg&& __rg)
227 : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg)))
228 { }
229
230 /**
231 * @brief Construct a queue from a range.
232 * @since C++23
233 */
234 template<__detail::__container_compatible_range<_Tp> _Rg,
235 typename _Alloc>
236 queue(from_range_t, _Rg&& __rg, const _Alloc& __a)
237 : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg), __a))
238 { }
239#endif
240
241 /**
242 * Returns true if the %queue is empty.
243 */
244 _GLIBCXX_NODISCARD bool
245 empty() const
246 { return c.empty(); }
247
248 /** Returns the number of elements in the %queue. */
249 _GLIBCXX_NODISCARD
250 size_type
251 size() const
252 { return c.size(); }
253
254 /**
255 * Returns a read/write reference to the data at the first
256 * element of the %queue.
257 */
258 _GLIBCXX_NODISCARD
259 reference
260 front()
261 {
262 __glibcxx_requires_nonempty();
263 return c.front();
264 }
265
266 /**
267 * Returns a read-only (constant) reference to the data at the first
268 * element of the %queue.
269 */
270 _GLIBCXX_NODISCARD
271 const_reference
272 front() const
273 {
274 __glibcxx_requires_nonempty();
275 return c.front();
276 }
277
278 /**
279 * Returns a read/write reference to the data at the last
280 * element of the %queue.
281 */
282 _GLIBCXX_NODISCARD
283 reference
284 back()
285 {
286 __glibcxx_requires_nonempty();
287 return c.back();
288 }
289
290 /**
291 * Returns a read-only (constant) reference to the data at the last
292 * element of the %queue.
293 */
294 _GLIBCXX_NODISCARD
295 const_reference
296 back() const
297 {
298 __glibcxx_requires_nonempty();
299 return c.back();
300 }
301
302 /**
303 * @brief Add data to the end of the %queue.
304 * @param __x Data to be added.
305 *
306 * This is a typical %queue operation. The function creates an
307 * element at the end of the %queue and assigns the given data
308 * to it. The time complexity of the operation depends on the
309 * underlying sequence.
310 */
311 void
312 push(const value_type& __x)
313 { c.push_back(__x); }
314
315#if __cplusplus >= 201103L
316 void
317 push(value_type&& __x)
318 { c.push_back(std::move(__x)); }
319
320#if __cplusplus > 201402L
321 template<typename... _Args>
322 decltype(auto)
323 emplace(_Args&&... __args)
324 { return c.emplace_back(std::forward<_Args>(__args)...); }
325#else
326 template<typename... _Args>
327 void
328 emplace(_Args&&... __args)
329 { c.emplace_back(std::forward<_Args>(__args)...); }
330#endif
331#endif
332
333#if __glibcxx_containers_ranges // C++ >= 23
334 template<__detail::__container_compatible_range<_Tp> _Rg>
335 void
336 push_range(_Rg&& __rg)
337 {
338 if constexpr (requires { c.append_range(std::forward<_Rg>(__rg)); })
339 c.append_range(std::forward<_Rg>(__rg));
340 else
341 ranges::copy(__rg, std::back_inserter(c));
342 }
343#endif
344
345 /**
346 * @brief Removes first element.
347 *
348 * This is a typical %queue operation. It shrinks the %queue by one.
349 * The time complexity of the operation depends on the underlying
350 * sequence.
351 *
352 * Note that no data is returned, and if the first element's
353 * data is needed, it should be retrieved before pop() is
354 * called.
355 */
356 void
357 pop()
358 {
359 __glibcxx_requires_nonempty();
360 c.pop_front();
361 }
362
363#if __cplusplus >= 201103L
364 void
365 swap(queue& __q)
366#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
367 noexcept(__is_nothrow_swappable<_Sequence>::value)
368#else
369 noexcept(__is_nothrow_swappable<_Tp>::value)
370#endif
371 {
372 using std::swap;
373 swap(c, __q.c);
374 }
375#endif // __cplusplus >= 201103L
376
377#if __glibcxx_format_ranges
378 friend class formatter<queue<_Tp, _Sequence>, char>;
379 friend class formatter<queue<_Tp, _Sequence>, wchar_t>;
380#endif
381 };
382
383#if __cpp_deduction_guides >= 201606
384 template<typename _Container,
385 typename = _RequireNotAllocator<_Container>>
386 queue(_Container) -> queue<typename _Container::value_type, _Container>;
387
388 template<typename _Container, typename _Allocator,
389 typename = _RequireNotAllocator<_Container>>
390 queue(_Container, _Allocator)
391 -> queue<typename _Container::value_type, _Container>;
392
393#ifdef __glibcxx_adaptor_iterator_pair_constructor
394 template<typename _InputIterator,
395 typename _ValT
396 = typename iterator_traits<_InputIterator>::value_type,
397 typename = _RequireInputIter<_InputIterator>>
398 queue(_InputIterator, _InputIterator) -> queue<_ValT>;
399
400 template<typename _InputIterator, typename _Allocator,
401 typename _ValT
402 = typename iterator_traits<_InputIterator>::value_type,
403 typename = _RequireInputIter<_InputIterator>,
404 typename = _RequireAllocator<_Allocator>>
405 queue(_InputIterator, _InputIterator, _Allocator)
406 -> queue<_ValT, deque<_ValT, _Allocator>>;
407#endif
408
409#if __glibcxx_containers_ranges // C++ >= 23
410 template<ranges::input_range _Rg>
411 queue(from_range_t, _Rg&&) -> queue<ranges::range_value_t<_Rg>>;
412
413 template<ranges::input_range _Rg, __allocator_like _Alloc>
414 queue(from_range_t, _Rg&&, _Alloc)
415 -> queue<ranges::range_value_t<_Rg>,
416 deque<ranges::range_value_t<_Rg>, _Alloc>>;
417#endif
418#endif
419
420 /**
421 * @brief Queue equality comparison.
422 * @param __x A %queue.
423 * @param __y A %queue of the same type as @a __x.
424 * @return True iff the size and elements of the queues are equal.
425 *
426 * This is an equivalence relation. Complexity and semantics depend on the
427 * underlying sequence type, but the expected rules are: this relation is
428 * linear in the size of the sequences, and queues are considered equivalent
429 * if their sequences compare equal.
430 */
431 template<typename _Tp, typename _Seq>
432 _GLIBCXX_NODISCARD
433 inline bool
434 operator==(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
435 { return __x.c == __y.c; }
436
437 /**
438 * @brief Queue ordering relation.
439 * @param __x A %queue.
440 * @param __y A %queue of the same type as @a x.
441 * @return True iff @a __x is lexicographically less than @a __y.
442 *
443 * This is an total ordering relation. Complexity and semantics
444 * depend on the underlying sequence type, but the expected rules
445 * are: this relation is linear in the size of the sequences, the
446 * elements must be comparable with @c <, and
447 * std::lexicographical_compare() is usually used to make the
448 * determination.
449 */
450 template<typename _Tp, typename _Seq>
451 _GLIBCXX_NODISCARD
452 inline bool
453 operator<(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
454 { return __x.c < __y.c; }
455
456 /// Based on operator==
457 template<typename _Tp, typename _Seq>
458 _GLIBCXX_NODISCARD
459 inline bool
460 operator!=(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
461 { return !(__x == __y); }
462
463 /// Based on operator<
464 template<typename _Tp, typename _Seq>
465 _GLIBCXX_NODISCARD
466 inline bool
467 operator>(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
468 { return __y < __x; }
469
470 /// Based on operator<
471 template<typename _Tp, typename _Seq>
472 _GLIBCXX_NODISCARD
473 inline bool
474 operator<=(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
475 { return !(__y < __x); }
476
477 /// Based on operator<
478 template<typename _Tp, typename _Seq>
479 _GLIBCXX_NODISCARD
480 inline bool
481 operator>=(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
482 { return !(__x < __y); }
483
484#if __cpp_lib_three_way_comparison
485 template<typename _Tp, three_way_comparable _Seq>
486 [[nodiscard]]
487 inline compare_three_way_result_t<_Seq>
488 operator<=>(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
489 { return __x.c <=> __y.c; }
490#endif
491
492#if __cplusplus >= 201103L
493 template<typename _Tp, typename _Seq>
494 inline
495#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
496 // Constrained free swap overload, see p0185r1
497 typename enable_if<__is_swappable<_Seq>::value>::type
498#else
499 void
500#endif
501 swap(queue<_Tp, _Seq>& __x, queue<_Tp, _Seq>& __y)
502 noexcept(noexcept(__x.swap(__y)))
503 { __x.swap(__y); }
504
505 template<typename _Tp, typename _Seq, typename _Alloc>
506 struct uses_allocator<queue<_Tp, _Seq>, _Alloc>
507 : public uses_allocator<_Seq, _Alloc>::type { };
508#endif // __cplusplus >= 201103L
509
510 /**
511 * @brief A standard container automatically sorting its contents.
512 *
513 * @ingroup sequences
514 *
515 * @tparam _Tp Type of element.
516 * @tparam _Sequence Type of underlying sequence, defaults to vector<_Tp>.
517 * @tparam _Compare Comparison function object type, defaults to
518 * less<_Sequence::value_type>.
519 *
520 * This is not a true container, but an @e adaptor. It holds
521 * another container, and provides a wrapper interface to that
522 * container. The wrapper is what enforces priority-based sorting
523 * and %queue behavior. Very few of the standard container/sequence
524 * interface requirements are met (e.g., iterators).
525 *
526 * The second template parameter defines the type of the underlying
527 * sequence/container. It defaults to std::vector, but it can be
528 * any type that supports @c front(), @c push_back, @c pop_back,
529 * and random-access iterators, such as std::deque or an
530 * appropriate user-defined type.
531 *
532 * The third template parameter supplies the means of making
533 * priority comparisons. It defaults to @c less<value_type> but
534 * can be anything defining a strict weak ordering.
535 *
536 * Members not found in @a normal containers are @c container_type,
537 * which is a typedef for the second Sequence parameter, and @c
538 * push, @c pop, and @c top, which are standard %queue operations.
539 *
540 * @note No equality/comparison operators are provided for
541 * %priority_queue.
542 *
543 * @note Sorting of the elements takes place as they are added to,
544 * and removed from, the %priority_queue using the
545 * %priority_queue's member functions. If you access the elements
546 * by other means, and change their data such that the sorting
547 * order would be different, the %priority_queue will not re-sort
548 * the elements for you. (How could it know to do so?)
549 */
550 template<typename _Tp, typename _Sequence = vector<_Tp>,
551 typename _Compare = less<typename _Sequence::value_type> >
552 class priority_queue
553 {
554#ifdef _GLIBCXX_CONCEPT_CHECKS
555 // concept requirements
556 typedef typename _Sequence::value_type _Sequence_value_type;
557# if __cplusplus < 201103L
558 __glibcxx_class_requires(_Tp, _SGIAssignableConcept)
559# endif
560 __glibcxx_class_requires(_Sequence, _SequenceConcept)
561 __glibcxx_class_requires(_Sequence, _RandomAccessContainerConcept)
562 __glibcxx_class_requires2(_Tp, _Sequence_value_type, _SameTypeConcept)
563 __glibcxx_class_requires4(_Compare, bool, _Tp, _Tp,
564 _BinaryFunctionConcept)
565#endif
566
567#if __cplusplus >= 201103L
568 template<typename _Alloc>
569 using _Uses = typename
570 enable_if<uses_allocator<_Sequence, _Alloc>::value>::type;
571
572#if __cplusplus >= 201703L
573 // _GLIBCXX_RESOLVE_LIB_DEFECTS
574 // 2566. Requirements on the first template parameter of container
575 // adaptors
576 static_assert(is_same<_Tp, typename _Sequence::value_type>::value,
577 "value_type must be the same as the underlying container");
578#endif // C++17
579#endif // C++11
580
581 public:
582 typedef typename _Sequence::value_type value_type;
583 typedef typename _Sequence::reference reference;
584 typedef typename _Sequence::const_reference const_reference;
585 typedef typename _Sequence::size_type size_type;
586 typedef _Sequence container_type;
587 // _GLIBCXX_RESOLVE_LIB_DEFECTS
588 // DR 2684. priority_queue lacking comparator typedef
589 typedef _Compare value_compare;
590
591 protected:
592 // See queue::c for notes on these names.
593 _Sequence c;
594 _Compare comp;
595
596 public:
597 /**
598 * @brief Default constructor creates no elements.
599 */
600#if __cplusplus < 201103L
601 explicit
602 priority_queue(const _Compare& __x = _Compare(),
603 const _Sequence& __s = _Sequence())
604 : c(__s), comp(__x)
605 { std::make_heap(c.begin(), c.end(), comp); }
606#else
607 template<typename _Seq = _Sequence, typename _Requires = typename
608 enable_if<__and_<is_default_constructible<_Compare>,
609 is_default_constructible<_Seq>>::value>::type>
610 priority_queue()
611 : c(), comp() { }
612
613 explicit
614 priority_queue(const _Compare& __x, const _Sequence& __s)
615 : c(__s), comp(__x)
616 { std::make_heap(c.begin(), c.end(), comp); }
617
618 explicit
619 priority_queue(const _Compare& __x, _Sequence&& __s = _Sequence())
620 : c(std::move(__s)), comp(__x)
621 { std::make_heap(c.begin(), c.end(), comp); }
622
623 priority_queue(const priority_queue&) = default;
624 priority_queue& operator=(const priority_queue&) = default;
625
626 priority_queue(priority_queue&& __q)
627 noexcept(__and_<is_nothrow_move_constructible<_Sequence>,
628 is_nothrow_move_constructible<_Compare>>::value)
629 : c(std::move(__q.c)), comp(std::move(__q.comp))
630 { __q.c.clear(); }
631
632 priority_queue&
633 operator=(priority_queue&& __q)
634 noexcept(__and_<is_nothrow_move_assignable<_Sequence>,
635 is_nothrow_move_assignable<_Compare>>::value)
636 {
637 c = std::move(__q.c);
638 __q.c.clear();
639 comp = std::move(__q.comp);
640 return *this;
641 }
642
643 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
644 explicit
645 priority_queue(const _Alloc& __a)
646 : c(__a), comp() { }
647
648 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
649 priority_queue(const _Compare& __x, const _Alloc& __a)
650 : c(__a), comp(__x) { }
651
652 // _GLIBCXX_RESOLVE_LIB_DEFECTS
653 // 2537. Constructors [...] taking allocators should call make_heap
654 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
655 priority_queue(const _Compare& __x, const _Sequence& __c,
656 const _Alloc& __a)
657 : c(__c, __a), comp(__x)
658 { std::make_heap(c.begin(), c.end(), comp); }
659
660 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
661 priority_queue(const _Compare& __x, _Sequence&& __c, const _Alloc& __a)
662 : c(std::move(__c), __a), comp(__x)
663 { std::make_heap(c.begin(), c.end(), comp); }
664
665 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
666 priority_queue(const priority_queue& __q, const _Alloc& __a)
667 : c(__q.c, __a), comp(__q.comp) { }
668
669 template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
670 priority_queue(priority_queue&& __q, const _Alloc& __a)
671 : c(std::move(__q.c), __a), comp(std::move(__q.comp))
672 { __q.c.clear(); }
673#endif
674
675 /**
676 * @brief Builds a %queue from a range.
677 * @param __first An input iterator.
678 * @param __last An input iterator.
679 * @param __x A comparison functor describing a strict weak ordering.
680 * @param __s An initial sequence with which to start.
681 *
682 * Begins by copying @a __s, inserting a copy of the elements
683 * from @a [first,last) into the copy of @a __s, then ordering
684 * the copy according to @a __x.
685 *
686 * For more information on function objects, see the
687 * documentation on @link functors functor base classes@endlink.
688 */
689#if __cplusplus < 201103L
690 template<typename _InputIterator>
691 priority_queue(_InputIterator __first, _InputIterator __last,
692 const _Compare& __x = _Compare(),
693 const _Sequence& __s = _Sequence())
694 : c(__s), comp(__x)
695 {
696 __glibcxx_requires_valid_range(__first, __last);
697 c.insert(c.end(), __first, __last);
698 std::make_heap(c.begin(), c.end(), comp);
699 }
700#else
701 // _GLIBCXX_RESOLVE_LIB_DEFECTS
702 // 3529. priority_queue(first, last) should construct c with (first, last)
703 template<typename _InputIterator,
704 typename = std::_RequireInputIter<_InputIterator>>
705 priority_queue(_InputIterator __first, _InputIterator __last,
706 const _Compare& __x = _Compare())
707 : c(__first, __last), comp(__x)
708 { std::make_heap(c.begin(), c.end(), comp); }
709
710 // _GLIBCXX_RESOLVE_LIB_DEFECTS
711 // 3522. Missing requirement on InputIterator template parameter
712 template<typename _InputIterator,
713 typename = std::_RequireInputIter<_InputIterator>>
714 priority_queue(_InputIterator __first, _InputIterator __last,
715 const _Compare& __x, const _Sequence& __s)
716 : c(__s), comp(__x)
717 {
718 __glibcxx_requires_valid_range(__first, __last);
719 c.insert(c.end(), __first, __last);
720 std::make_heap(c.begin(), c.end(), comp);
721 }
722
723 template<typename _InputIterator,
724 typename = std::_RequireInputIter<_InputIterator>>
725 priority_queue(_InputIterator __first, _InputIterator __last,
726 const _Compare& __x, _Sequence&& __s)
727 : c(std::move(__s)), comp(__x)
728 {
729 __glibcxx_requires_valid_range(__first, __last);
730 c.insert(c.end(), __first, __last);
731 std::make_heap(c.begin(), c.end(), comp);
732 }
733
734 // _GLIBCXX_RESOLVE_LIB_DEFECTS
735 // 3506. Missing allocator-extended constructors for priority_queue
736 template<typename _InputIterator, typename _Alloc,
737 typename = std::_RequireInputIter<_InputIterator>,
738 typename _Requires = _Uses<_Alloc>>
739 priority_queue(_InputIterator __first, _InputIterator __last,
740 const _Alloc& __alloc)
741 : c(__first, __last, __alloc), comp()
742 { std::make_heap(c.begin(), c.end(), comp); }
743
744 template<typename _InputIterator, typename _Alloc,
745 typename = std::_RequireInputIter<_InputIterator>,
746 typename _Requires = _Uses<_Alloc>>
747 priority_queue(_InputIterator __first, _InputIterator __last,
748 const _Compare& __x, const _Alloc& __alloc)
749 : c(__first, __last, __alloc), comp(__x)
750 { std::make_heap(c.begin(), c.end(), comp); }
751
752 template<typename _InputIterator, typename _Alloc,
753 typename = std::_RequireInputIter<_InputIterator>,
754 typename _Requires = _Uses<_Alloc>>
755 priority_queue(_InputIterator __first, _InputIterator __last,
756 const _Compare& __x, const _Sequence& __s,
757 const _Alloc& __alloc)
758 : c(__s, __alloc), comp(__x)
759 {
760 __glibcxx_requires_valid_range(__first, __last);
761 c.insert(c.end(), __first, __last);
762 std::make_heap(c.begin(), c.end(), comp);
763 }
764
765 template<typename _InputIterator, typename _Alloc,
766 typename _Requires = _Uses<_Alloc>>
767 priority_queue(_InputIterator __first, _InputIterator __last,
768 const _Compare& __x, _Sequence&& __s,
769 const _Alloc& __alloc)
770 : c(std::move(__s), __alloc), comp(__x)
771 {
772 __glibcxx_requires_valid_range(__first, __last);
773 c.insert(c.end(), __first, __last);
774 std::make_heap(c.begin(), c.end(), comp);
775 }
776#endif
777
778#if __glibcxx_containers_ranges // C++ >= 23
779 /**
780 * @brief Construct a priority_queue from a range.
781 * @since C++23
782 *
783 * @{
784 */
785 template<__detail::__container_compatible_range<_Tp> _Rg>
786 priority_queue(from_range_t, _Rg&& __rg,
787 const _Compare& __x = _Compare())
788 : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg))), comp(__x)
789 { std::make_heap(c.begin(), c.end(), comp); }
790
791 template<__detail::__container_compatible_range<_Tp> _Rg, typename _Alloc>
792 priority_queue(from_range_t, _Rg&& __rg, const _Compare& __x,
793 const _Alloc& __a)
794 : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg), __a)), comp(__x)
795 { std::make_heap(c.begin(), c.end(), comp); }
796
797 template<__detail::__container_compatible_range<_Tp> _Rg, typename _Alloc>
798 priority_queue(from_range_t, _Rg&& __rg, const _Alloc& __a)
799 : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg), __a)), comp()
800 { std::make_heap(c.begin(), c.end(), comp); }
801 /// @}
802#endif
803
804 /**
805 * Returns true if the %queue is empty.
806 */
807 _GLIBCXX_NODISCARD bool
808 empty() const
809 { return c.empty(); }
810
811 /** Returns the number of elements in the %queue. */
812 _GLIBCXX_NODISCARD
813 size_type
814 size() const
815 { return c.size(); }
816
817 /**
818 * Returns a read-only (constant) reference to the data at the first
819 * element of the %queue.
820 */
821 _GLIBCXX_NODISCARD
822 const_reference
823 top() const
824 {
825 __glibcxx_requires_nonempty();
826 return c.front();
827 }
828
829 /**
830 * @brief Add data to the %queue.
831 * @param __x Data to be added.
832 *
833 * This is a typical %queue operation.
834 * The time complexity of the operation depends on the underlying
835 * sequence.
836 */
837 void
838 push(const value_type& __x)
839 {
840 c.push_back(__x);
841 std::push_heap(c.begin(), c.end(), comp);
842 }
843
844#if __cplusplus >= 201103L
845 void
846 push(value_type&& __x)
847 {
848 c.push_back(std::move(__x));
849 std::push_heap(c.begin(), c.end(), comp);
850 }
851
852 template<typename... _Args>
853 void
854 emplace(_Args&&... __args)
855 {
856 c.emplace_back(std::forward<_Args>(__args)...);
857 std::push_heap(c.begin(), c.end(), comp);
858 }
859#endif
860
861#if __glibcxx_containers_ranges // C++ >= 23
862 template<__detail::__container_compatible_range<_Tp> _Rg>
863 void
864 push_range(_Rg&& __rg)
865 {
866 if constexpr (requires { c.append_range(std::forward<_Rg>(__rg)); })
867 c.append_range(std::forward<_Rg>(__rg));
868 else
869 ranges::copy(__rg, std::back_inserter(c));
870 std::make_heap(c.begin(), c.end(), comp);
871 }
872#endif
873
874 /**
875 * @brief Removes first element.
876 *
877 * This is a typical %queue operation. It shrinks the %queue
878 * by one. The time complexity of the operation depends on the
879 * underlying sequence.
880 *
881 * Note that no data is returned, and if the first element's
882 * data is needed, it should be retrieved before pop() is
883 * called.
884 */
885 void
886 pop()
887 {
888 __glibcxx_requires_nonempty();
889 std::pop_heap(c.begin(), c.end(), comp);
890 c.pop_back();
891 }
892
893#if __cplusplus >= 201103L
894 void
895 swap(priority_queue& __pq)
896 noexcept(__and_<
897#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
898 __is_nothrow_swappable<_Sequence>,
899#else
900 __is_nothrow_swappable<_Tp>,
901#endif
902 __is_nothrow_swappable<_Compare>
903 >::value)
904 {
905 using std::swap;
906 swap(c, __pq.c);
907 swap(comp, __pq.comp);
908 }
909#endif // __cplusplus >= 201103L
910
911#if __glibcxx_format_ranges
912 friend class formatter<priority_queue<_Tp, _Sequence, _Compare>, char>;
913 friend class formatter<priority_queue<_Tp, _Sequence, _Compare>, wchar_t>;
914#endif
915 };
916
917#if __cpp_deduction_guides >= 201606
918 template<typename _Compare, typename _Container,
919 typename = _RequireNotAllocator<_Compare>,
920 typename = _RequireNotAllocator<_Container>>
921 priority_queue(_Compare, _Container)
922 -> priority_queue<typename _Container::value_type, _Container, _Compare>;
923
924 template<typename _InputIterator, typename _ValT
925 = typename iterator_traits<_InputIterator>::value_type,
926 typename _Compare = less<_ValT>,
927 typename _Container = vector<_ValT>,
928 typename = _RequireInputIter<_InputIterator>,
929 typename = _RequireNotAllocator<_Compare>,
930 typename = _RequireNotAllocator<_Container>>
931 priority_queue(_InputIterator, _InputIterator, _Compare = _Compare(),
932 _Container = _Container())
933 -> priority_queue<_ValT, _Container, _Compare>;
934
935 template<typename _Compare, typename _Container, typename _Allocator,
936 typename = _RequireNotAllocator<_Compare>,
937 typename = _RequireNotAllocator<_Container>>
938 priority_queue(_Compare, _Container, _Allocator)
939 -> priority_queue<typename _Container::value_type, _Container, _Compare>;
940
941#if __glibcxx_containers_ranges // C++ >= 23
942 template<ranges::input_range _Rg,
943 __not_allocator_like _Compare = less<ranges::range_value_t<_Rg>>,
944 __allocator_like _Alloc = std::allocator<ranges::range_value_t<_Rg>>>
945 priority_queue(from_range_t, _Rg&&, _Compare = _Compare(),
946 _Alloc = _Alloc())
947 -> priority_queue<ranges::range_value_t<_Rg>,
948 vector<ranges::range_value_t<_Rg>, _Alloc>,
949 _Compare>;
950
951 template<ranges::input_range _Rg, __allocator_like _Alloc>
952 priority_queue(from_range_t, _Rg&&, _Alloc)
953 -> priority_queue<ranges::range_value_t<_Rg>,
954 vector<ranges::range_value_t<_Rg>, _Alloc>>;
955#endif
956#endif
957
958 // No equality/comparison operators are provided for priority_queue.
959
960#if __cplusplus >= 201103L
961 template<typename _Tp, typename _Sequence, typename _Compare>
962 inline
963#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
964 // Constrained free swap overload, see p0185r1
965 typename enable_if<__and_<__is_swappable<_Sequence>,
966 __is_swappable<_Compare>>::value>::type
967#else
968 void
969#endif
970 swap(priority_queue<_Tp, _Sequence, _Compare>& __x,
971 priority_queue<_Tp, _Sequence, _Compare>& __y)
972 noexcept(noexcept(__x.swap(__y)))
973 { __x.swap(__y); }
974
975 template<typename _Tp, typename _Sequence, typename _Compare,
976 typename _Alloc>
977 struct uses_allocator<priority_queue<_Tp, _Sequence, _Compare>, _Alloc>
978 : public uses_allocator<_Sequence, _Alloc>::type { };
979#endif // __cplusplus >= 201103L
980
981_GLIBCXX_END_NAMESPACE_VERSION
982} // namespace
983
984#endif /* _STL_QUEUE_H */
985