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79d08e398c
https://en.wikipedia.org/wiki/Heapsort#Bottom-up_heapsort In `pop_heap` specifically, the item we insert at the top and sift downward is guaranteed to be leaf-sized, so we expect it to go pretty far down. Sift it down as if it were INT_MIN, and then bubble it back up if needed. Also known as "heapsort with bounce." Numbers are here: https://godbolt.org/z/cvfnYW6fe Fixes #10008. Differential Revision: https://reviews.llvm.org/D118003
70 lines
2.3 KiB
C++
70 lines
2.3 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ALGORITHM_POP_HEAP_H
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#define _LIBCPP___ALGORITHM_POP_HEAP_H
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#include <__algorithm/comp.h>
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#include <__algorithm/comp_ref_type.h>
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#include <__algorithm/push_heap.h>
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#include <__algorithm/sift_down.h>
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#include <__config>
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#include <__iterator/iterator_traits.h>
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#include <__utility/move.h>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <class _Compare, class _RandomAccessIterator>
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inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
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void
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__pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
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typename iterator_traits<_RandomAccessIterator>::difference_type __len)
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{
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using value_type = typename iterator_traits<_RandomAccessIterator>::value_type;
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if (__len > 1)
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{
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value_type __top = std::move(*__first); // create a hole at __first
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_RandomAccessIterator __hole = std::__floyd_sift_down<_Compare>(__first, __comp, __len);
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--__last;
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if (__hole == __last) {
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*__hole = std::move(__top);
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} else {
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*__hole = std::move(*__last);
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++__hole;
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*__last = std::move(__top);
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std::__sift_up<_Compare>(__first, __hole, __comp, __hole - __first);
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}
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}
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}
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template <class _RandomAccessIterator, class _Compare>
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inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
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void
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pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
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{
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typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
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_VSTD::__pop_heap<_Comp_ref>(__first, __last, __comp, __last - __first);
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}
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template <class _RandomAccessIterator>
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inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
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void
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pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
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{
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_VSTD::pop_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
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}
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___ALGORITHM_POP_HEAP_H
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