libcxx/include/__algorithm/partial_sort.h

   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_PARTIAL_SORT_H
  10 #define _LIBCPP___ALGORITHM_PARTIAL_SORT_H
  11
  12 #include <__algorithm/comp.h>
  13 #include <__algorithm/comp_ref_type.h>
  14 #include <__algorithm/iterator_operations.h>
  15 #include <__algorithm/make_heap.h>
  16 #include <__algorithm/sift_down.h>
  17 #include <__algorithm/sort_heap.h>
  18 #include <__config>
  19 #include <__debug_utils/randomize_range.h>
  20 #include <__iterator/iterator_traits.h>
  21 #include <__type_traits/is_copy_assignable.h>
  22 #include <__type_traits/is_copy_constructible.h>
  23 #include <__utility/move.h>
  24
  25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  26 #  pragma GCC system_header
  27 #endif
  28
  29 _LIBCPP_BEGIN_NAMESPACE_STD
  30
  31 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator, class _Sentinel>
  32 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  33 _RandomAccessIterator __partial_sort_impl(
  34     _RandomAccessIterator __first, _RandomAccessIterator __middle, _Sentinel __last, _Compare&& __comp) {
  35   if (__first == __middle) {
  36     return _IterOps<_AlgPolicy>::next(__middle, __last);
  37   }
  38
  39   std::__make_heap<_AlgPolicy>(__first, __middle, __comp);
  40
  41   typename iterator_traits<_RandomAccessIterator>::difference_type __len = __middle - __first;
  42   _RandomAccessIterator __i = __middle;
  43   for (; __i != __last; ++__i)
  44   {
  45       if (__comp(*__i, *__first))
  46       {
  47           _IterOps<_AlgPolicy>::iter_swap(__i, __first);
  48           std::__sift_down<_AlgPolicy>(__first, __comp, __len, __first);
  49       }
  50   }
  51   std::__sort_heap<_AlgPolicy>(std::move(__first), std::move(__middle), __comp);
  52
  53   return __i;
  54 }
  55
  56 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator, class _Sentinel>
  57 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  58 _RandomAccessIterator __partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _Sentinel __last,
  59                                      _Compare& __comp) {
  60   if (__first == __middle)
  61       return _IterOps<_AlgPolicy>::next(__middle, __last);
  62
  63   std::__debug_randomize_range<_AlgPolicy>(__first, __last);
  64
  65   auto __last_iter =
  66       std::__partial_sort_impl<_AlgPolicy>(__first, __middle, __last, static_cast<__comp_ref_type<_Compare> >(__comp));
  67
  68   std::__debug_randomize_range<_AlgPolicy>(__middle, __last);
  69
  70   return __last_iter;
  71 }
  72
  73 template <class _RandomAccessIterator, class _Compare>
  74 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
  75 void
  76 partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last,
  77              _Compare __comp)
  78 {
  79   static_assert(std::is_copy_constructible<_RandomAccessIterator>::value, "Iterators must be copy constructible.");
  80   static_assert(std::is_copy_assignable<_RandomAccessIterator>::value, "Iterators must be copy assignable.");
  81
  82   (void)std::__partial_sort<_ClassicAlgPolicy>(std::move(__first), std::move(__middle), std::move(__last), __comp);
  83 }
  84
  85 template <class _RandomAccessIterator>
  86 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
  87 void
  88 partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last)
  89 {
  90     _VSTD::partial_sort(__first, __middle, __last, __less<>());
  91 }
  92
  93 _LIBCPP_END_NAMESPACE_STD
  94
  95 #endif // _LIBCPP___ALGORITHM_PARTIAL_SORT_H