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> 20 #include <__debug_utils/randomize_range.h> 21 #include <__iterator/iterator_traits.h> 22 #include <__utility/move.h> 23 #include <type_traits> 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_CONSTEXPR_AFTER_CXX17 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, _Compare>(__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, _Compare>(__first, __comp, __len, __first); 49 } 50 51 } 52 std::__sort_heap<_AlgPolicy, _Compare>(std::move(__first), std::move(__middle), __comp); 53 54 return __i; 55 } 56 57 // TODO(ranges): once `ranges::shuffle` is implemented, remove this helper and make `__debug_randomize_range` support 58 // sentinels. 59 template <class _AlgPolicy, class _RandomAccessIterator, class _Sentinel> 60 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 61 void __maybe_randomize(_RandomAccessIterator __first, _Sentinel __last) { 62 std::__debug_randomize_range<_AlgPolicy>(__first, _IterOps<_AlgPolicy>::next(__first, __last)); 63 } 64 65 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator, class _Sentinel> 66 _LIBCPP_CONSTEXPR_AFTER_CXX17 67 _RandomAccessIterator __partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _Sentinel __last, 68 _Compare& __comp) { 69 if (__first == __middle) 70 return _IterOps<_AlgPolicy>::next(__middle, __last); 71 72 std::__maybe_randomize<_AlgPolicy>(__first, __last); 73 74 using _Comp_ref = typename __comp_ref_type<_Compare>::type; 75 auto __last_iter = std::__partial_sort_impl<_AlgPolicy, _Comp_ref>(__first, __middle, __last, __comp); 76 77 std::__maybe_randomize<_AlgPolicy>(__middle, __last); 78 79 return __last_iter; 80 } 81 82 template <class _RandomAccessIterator, class _Compare> 83 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 84 void 85 partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last, 86 _Compare __comp) 87 { 88 static_assert(std::is_copy_constructible<_RandomAccessIterator>::value, "Iterators must be copy constructible."); 89 static_assert(std::is_copy_assignable<_RandomAccessIterator>::value, "Iterators must be copy assignable."); 90 91 (void)std::__partial_sort<_ClassicAlgPolicy>(std::move(__first), std::move(__middle), std::move(__last), __comp); 92 } 93 94 template <class _RandomAccessIterator> 95 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 96 void 97 partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last) 98 { 99 _VSTD::partial_sort(__first, __middle, __last, 100 __less<typename iterator_traits<_RandomAccessIterator>::value_type>()); 101 } 102 103 _LIBCPP_END_NAMESPACE_STD 104 105 #endif // _LIBCPP___ALGORITHM_PARTIAL_SORT_H 106