v1/__algorithm/rotate.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___ALGORITHM_ROTATE_H
0010 #define _LIBCPP___ALGORITHM_ROTATE_H
0011
0012 #include <__algorithm/iterator_operations.h>
0013 #include <__algorithm/move.h>
0014 #include <__algorithm/move_backward.h>
0015 #include <__algorithm/swap_ranges.h>
0016 #include <__config>
0017 #include <__iterator/iterator_traits.h>
0018 #include <__type_traits/is_trivially_assignable.h>
0019 #include <__utility/move.h>
0020 #include <__utility/pair.h>
0021
0022 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0023 #  pragma GCC system_header
0024 #endif
0025
0026 _LIBCPP_PUSH_MACROS
0027 #include <__undef_macros>
0028
0029 _LIBCPP_BEGIN_NAMESPACE_STD
0030
0031 template <class _AlgPolicy, class _ForwardIterator>
0032 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
0033 __rotate_left(_ForwardIterator __first, _ForwardIterator __last) {
0034   typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
0035   using _Ops = _IterOps<_AlgPolicy>;
0036
0037   value_type __tmp       = _Ops::__iter_move(__first);
0038   _ForwardIterator __lm1 = std::__move<_AlgPolicy>(_Ops::next(__first), __last, __first).second;
0039   *__lm1                 = std::move(__tmp);
0040   return __lm1;
0041 }
0042
0043 template <class _AlgPolicy, class _BidirectionalIterator>
0044 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _BidirectionalIterator
0045 __rotate_right(_BidirectionalIterator __first, _BidirectionalIterator __last) {
0046   typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
0047   using _Ops = _IterOps<_AlgPolicy>;
0048
0049   _BidirectionalIterator __lm1 = _Ops::prev(__last);
0050   value_type __tmp             = _Ops::__iter_move(__lm1);
0051   _BidirectionalIterator __fp1 = std::__move_backward<_AlgPolicy>(__first, __lm1, std::move(__last)).second;
0052   *__first                     = std::move(__tmp);
0053   return __fp1;
0054 }
0055
0056 template <class _AlgPolicy, class _ForwardIterator>
0057 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _ForwardIterator
0058 __rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last) {
0059   _ForwardIterator __i = __middle;
0060   while (true) {
0061     _IterOps<_AlgPolicy>::iter_swap(__first, __i);
0062     ++__first;
0063     if (++__i == __last)
0064       break;
0065     if (__first == __middle)
0066       __middle = __i;
0067   }
0068   _ForwardIterator __r = __first;
0069   if (__first != __middle) {
0070     __i = __middle;
0071     while (true) {
0072       _IterOps<_AlgPolicy>::iter_swap(__first, __i);
0073       ++__first;
0074       if (++__i == __last) {
0075         if (__first == __middle)
0076           break;
0077         __i = __middle;
0078       } else if (__first == __middle)
0079         __middle = __i;
0080     }
0081   }
0082   return __r;
0083 }
0084
0085 template <typename _Integral>
0086 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _Integral __algo_gcd(_Integral __x, _Integral __y) {
0087   do {
0088     _Integral __t = __x % __y;
0089     __x           = __y;
0090     __y           = __t;
0091   } while (__y);
0092   return __x;
0093 }
0094
0095 template <class _AlgPolicy, typename _RandomAccessIterator>
0096 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _RandomAccessIterator
0097 __rotate_gcd(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last) {
0098   typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
0099   typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
0100   using _Ops = _IterOps<_AlgPolicy>;
0101
0102   const difference_type __m1 = __middle - __first;
0103   const difference_type __m2 = _Ops::distance(__middle, __last);
0104   if (__m1 == __m2) {
0105     std::__swap_ranges<_AlgPolicy>(__first, __middle, __middle, __last);
0106     return __middle;
0107   }
0108   const difference_type __g = std::__algo_gcd(__m1, __m2);
0109   for (_RandomAccessIterator __p = __first + __g; __p != __first;) {
0110     value_type __t(_Ops::__iter_move(--__p));
0111     _RandomAccessIterator __p1 = __p;
0112     _RandomAccessIterator __p2 = __p1 + __m1;
0113     do {
0114       *__p1                     = _Ops::__iter_move(__p2);
0115       __p1                      = __p2;
0116       const difference_type __d = _Ops::distance(__p2, __last);
0117       if (__m1 < __d)
0118         __p2 += __m1;
0119       else
0120         __p2 = __first + (__m1 - __d);
0121     } while (__p2 != __p);
0122     *__p1 = std::move(__t);
0123   }
0124   return __first + __m2;
0125 }
0126
0127 template <class _AlgPolicy, class _ForwardIterator>
0128 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
0129 __rotate_impl(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last, std::forward_iterator_tag) {
0130   typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
0131   if (is_trivially_move_assignable<value_type>::value) {
0132     if (_IterOps<_AlgPolicy>::next(__first) == __middle)
0133       return std::__rotate_left<_AlgPolicy>(__first, __last);
0134   }
0135   return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
0136 }
0137
0138 template <class _AlgPolicy, class _BidirectionalIterator>
0139 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _BidirectionalIterator __rotate_impl(
0140     _BidirectionalIterator __first,
0141     _BidirectionalIterator __middle,
0142     _BidirectionalIterator __last,
0143     bidirectional_iterator_tag) {
0144   typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
0145   if (is_trivially_move_assignable<value_type>::value) {
0146     if (_IterOps<_AlgPolicy>::next(__first) == __middle)
0147       return std::__rotate_left<_AlgPolicy>(__first, __last);
0148     if (_IterOps<_AlgPolicy>::next(__middle) == __last)
0149       return std::__rotate_right<_AlgPolicy>(__first, __last);
0150   }
0151   return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
0152 }
0153
0154 template <class _AlgPolicy, class _RandomAccessIterator>
0155 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _RandomAccessIterator __rotate_impl(
0156     _RandomAccessIterator __first,
0157     _RandomAccessIterator __middle,
0158     _RandomAccessIterator __last,
0159     random_access_iterator_tag) {
0160   typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
0161   if (is_trivially_move_assignable<value_type>::value) {
0162     if (_IterOps<_AlgPolicy>::next(__first) == __middle)
0163       return std::__rotate_left<_AlgPolicy>(__first, __last);
0164     if (_IterOps<_AlgPolicy>::next(__middle) == __last)
0165       return std::__rotate_right<_AlgPolicy>(__first, __last);
0166     return std::__rotate_gcd<_AlgPolicy>(__first, __middle, __last);
0167   }
0168   return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
0169 }
0170
0171 template <class _AlgPolicy, class _Iterator, class _Sentinel>
0172 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iterator, _Iterator>
0173 __rotate(_Iterator __first, _Iterator __middle, _Sentinel __last) {
0174   using _Ret            = pair<_Iterator, _Iterator>;
0175   _Iterator __last_iter = _IterOps<_AlgPolicy>::next(__middle, __last);
0176
0177   if (__first == __middle)
0178     return _Ret(__last_iter, __last_iter);
0179   if (__middle == __last)
0180     return _Ret(std::move(__first), std::move(__last_iter));
0181
0182   using _IterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_Iterator>;
0183   auto __result = std::__rotate_impl<_AlgPolicy>(std::move(__first), std::move(__middle), __last_iter, _IterCategory());
0184
0185   return _Ret(std::move(__result), std::move(__last_iter));
0186 }
0187
0188 template <class _ForwardIterator>
0189 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
0190 rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last) {
0191   return std::__rotate<_ClassicAlgPolicy>(std::move(__first), std::move(__middle), std::move(__last)).first;
0192 }
0193
0194 _LIBCPP_END_NAMESPACE_STD
0195
0196 _LIBCPP_POP_MACROS
0197
0198 #endif // _LIBCPP___ALGORITHM_ROTATE_H