1//===----------------------------------------------------------------------===//
 2//
 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 4// See https://llvm.org/LICENSE.txt for license information.
 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 6//
 7//===----------------------------------------------------------------------===//
 8
 9#ifndef _LIBCPP___ALGORITHM_NEXT_PERMUTATION_H
10#define _LIBCPP___ALGORITHM_NEXT_PERMUTATION_H
11
12#include <__algorithm/comp.h>
13#include <__algorithm/comp_ref_type.h>
14#include <__algorithm/iterator_operations.h>
15#include <__algorithm/reverse.h>
16#include <__config>
17#include <__iterator/iterator_traits.h>
18#include <__utility/move.h>
19#include <__utility/pair.h>
20
21#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
22#  pragma GCC system_header
23#endif
24
25_LIBCPP_PUSH_MACROS
26#include <__undef_macros>
27
28_LIBCPP_BEGIN_NAMESPACE_STD
29
30template <class _AlgPolicy, class _Compare, class _BidirectionalIterator, class _Sentinel>
31_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator, bool>
32__next_permutation(_BidirectionalIterator __first, _Sentinel __last, _Compare&& __comp) {
33  using _Result = pair<_BidirectionalIterator, bool>;
34
35  _BidirectionalIterator __last_iter = _IterOps<_AlgPolicy>::next(__first, __last);
36  _BidirectionalIterator __i         = __last_iter;
37  if (__first == __last || __first == --__i)
38    return _Result(std::move(__last_iter), false);
39
40  while (true) {
41    _BidirectionalIterator __ip1 = __i;
42    if (__comp(*--__i, *__ip1)) {
43      _BidirectionalIterator __j = __last_iter;
44      while (!__comp(*__i, *--__j))
45        ;
46      _IterOps<_AlgPolicy>::iter_swap(__i, __j);
47      std::__reverse<_AlgPolicy>(__ip1, __last_iter);
48      return _Result(std::move(__last_iter), true);
49    }
50    if (__i == __first) {
51      std::__reverse<_AlgPolicy>(__first, __last_iter);
52      return _Result(std::move(__last_iter), false);
53    }
54  }
55}
56
57template <class _BidirectionalIterator, class _Compare>
58inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
59next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp) {
60  return std::__next_permutation<_ClassicAlgPolicy>(
61             std::move(__first), std::move(__last), static_cast<__comp_ref_type<_Compare> >(__comp))
62      .second;
63}
64
65template <class _BidirectionalIterator>
66inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
67next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last) {
68  return std::next_permutation(__first, __last, __less<>());
69}
70
71_LIBCPP_END_NAMESPACE_STD
72
73_LIBCPP_POP_MACROS
74
75#endif // _LIBCPP___ALGORITHM_NEXT_PERMUTATION_H