134723edd5
This is a fairly mechanical change, it just moves each algorithm into its own header. This is intended to be a NFC. This commit re-applies 7ed7d4ccb899, which was reverted in 692d7166f771 because the Modules build got broken. The modules build has now been fixed, so we're re-committing this. Differential Revision: https://reviews.llvm.org/D103583 Attribution note ---------------- I'm only committing this. This commit is a mix of D103583, D103330 and D104171 authored by: Co-authored-by: Christopher Di Bella <cjdb@google.com> Co-authored-by: zoecarver <z.zoelec2@gmail.com>
86 lines
2.6 KiB
C++
86 lines
2.6 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_SIFT_DOWN_H
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#define _LIBCPP___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>
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#include <type_traits>
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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_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <class _Compare, class _RandomAccessIterator>
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_LIBCPP_CONSTEXPR_AFTER_CXX11 void
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__sift_down(_RandomAccessIterator __first, _RandomAccessIterator /*__last*/,
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_Compare __comp,
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typename iterator_traits<_RandomAccessIterator>::difference_type __len,
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_RandomAccessIterator __start)
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{
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typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
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typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
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// left-child of __start is at 2 * __start + 1
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// right-child of __start is at 2 * __start + 2
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difference_type __child = __start - __first;
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if (__len < 2 || (__len - 2) / 2 < __child)
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return;
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__child = 2 * __child + 1;
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_RandomAccessIterator __child_i = __first + __child;
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if ((__child + 1) < __len && __comp(*__child_i, *(__child_i + 1))) {
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// right-child exists and is greater than left-child
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++__child_i;
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++__child;
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}
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// check if we are in heap-order
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if (__comp(*__child_i, *__start))
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// we are, __start is larger than it's largest child
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return;
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value_type __top(_VSTD::move(*__start));
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do
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{
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// we are not in heap-order, swap the parent with its largest child
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*__start = _VSTD::move(*__child_i);
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__start = __child_i;
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if ((__len - 2) / 2 < __child)
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break;
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// recompute the child based off of the updated parent
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__child = 2 * __child + 1;
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__child_i = __first + __child;
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if ((__child + 1) < __len && __comp(*__child_i, *(__child_i + 1))) {
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// right-child exists and is greater than left-child
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++__child_i;
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++__child;
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}
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// check if we are in heap-order
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} while (!__comp(*__child_i, __top));
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*__start = _VSTD::move(__top);
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}
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___ALGORITHM_SIFT_DOWN_H
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