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_BEGIN_NAMESPACE_STD
26
27template <class _AlgPolicy, class _Compare, class _BidirectionalIterator, class _Sentinel>
28_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator, bool>
29__next_permutation(_BidirectionalIterator __first, _Sentinel __last, _Compare&& __comp)
30{
31    using _Result = pair<_BidirectionalIterator, bool>;
32
33    _BidirectionalIterator __last_iter = _IterOps<_AlgPolicy>::next(__first, __last);
34    _BidirectionalIterator __i = __last_iter;
35    if (__first == __last || __first == --__i)
36        return _Result(std::move(__last_iter), false);
37
38    while (true)
39    {
40        _BidirectionalIterator __ip1 = __i;
41        if (__comp(*--__i, *__ip1))
42        {
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        {
52            std::__reverse<_AlgPolicy>(__first, __last_iter);
53            return _Result(std::move(__last_iter), false);
54        }
55    }
56}
57
58template <class _BidirectionalIterator, class _Compare>
59inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
60bool
61next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp)
62{
63  return std::__next_permutation<_ClassicAlgPolicy>(
64      std::move(__first), std::move(__last), static_cast<__comp_ref_type<_Compare> >(__comp)).second;
65}
66
67template <class _BidirectionalIterator>
68inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
69bool
70next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last)
71{
72    return _VSTD::next_permutation(__first, __last,
73                                  __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
74}
75
76_LIBCPP_END_NAMESPACE_STD
77
78#endif // _LIBCPP___ALGORITHM_NEXT_PERMUTATION_H
79