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 
27 template <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 
58 template <class _BidirectionalIterator, class _Compare>
59 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
60 bool
61 next_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 
67 template <class _BidirectionalIterator>
68 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
69 bool
70 next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last)
71 {
72     return _VSTD::next_permutation(__first, __last, __less<>());
73 }
74 
75 _LIBCPP_END_NAMESPACE_STD
76 
77 #endif // _LIBCPP___ALGORITHM_NEXT_PERMUTATION_H
78