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_PREV_PERMUTATION_H
10 #define _LIBCPP___ALGORITHM_PREV_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 
30 template <class _AlgPolicy, class _Compare, class _BidirectionalIterator, class _Sentinel>
31 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator, bool>
32 __prev_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(*__ip1, *--__i)) {
43       _BidirectionalIterator __j = __last_iter;
44       while (!__comp(*--__j, *__i))
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 
57 template <class _BidirectionalIterator, class _Compare>
58 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
59 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp) {
60   return std::__prev_permutation<_ClassicAlgPolicy>(
61              std::move(__first), std::move(__last), static_cast<__comp_ref_type<_Compare> >(__comp))
62       .second;
63 }
64 
65 template <class _BidirectionalIterator>
66 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
67 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last) {
68   return std::prev_permutation(__first, __last, __less<>());
69 }
70 
71 _LIBCPP_END_NAMESPACE_STD
72 
73 _LIBCPP_POP_MACROS
74 
75 #endif // _LIBCPP___ALGORITHM_PREV_PERMUTATION_H
76