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77 lines
2.5 KiB
C++
77 lines
2.5 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Span.h>
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#include <AK/StdLibExtras.h>
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#include <AK/Types.h>
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namespace AK {
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template<typename T>
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int integral_compare(const T& a, const T& b)
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{
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return a - b;
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}
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template<typename T, typename Compare>
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T* binary_search(Span<T> haystack, const T& needle, Compare compare = integral_compare, size_t* nearby_index = nullptr)
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{
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if (haystack.size() == 0) {
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if (nearby_index)
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*nearby_index = 0;
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return nullptr;
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}
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size_t low = 0;
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size_t high = haystack.size() - 1;
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while (low <= high) {
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size_t middle = low + ((high - low) / 2);
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int comparison = compare(needle, haystack[middle]);
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if (comparison < 0)
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if (middle != 0)
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high = middle - 1;
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else
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break;
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else if (comparison > 0)
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low = middle + 1;
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else {
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if (nearby_index)
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*nearby_index = middle;
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return &haystack[middle];
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}
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}
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if (nearby_index)
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*nearby_index = min(low, high);
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return nullptr;
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}
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}
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using AK::binary_search;
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