57 lines
1.6 KiB
C++
57 lines
1.6 KiB
C++
/**
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This file is a part of rexy's general purpose library
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Copyright (C) 2020 rexy712
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef REXY_CX_ALGORITHM_HPP
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#define REXY_CX_ALGORITHM_HPP
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#include "utility.hpp" //swap
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namespace rexy::cx{
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template<class Iter, class Compare>
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constexpr Iter qs_partition(Iter left, Iter right, const Compare& cmp){
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auto range = right - left;
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auto pivot = left + (range / 2);
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auto value = *pivot;
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//move pivot value all the way to the right side to preserve it
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cx::swap(*pivot, *right);
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for(auto it = left;it != right;++it){
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if(cmp(*it, value)){
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cx::swap(*left, *it);
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++left;
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}
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}
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//move pivot value back to proper position
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cx::swap(*left, *right);
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return left;
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}
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template<class Iter, class Compare>
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constexpr void quicksort(Iter left, Iter right, const Compare& cmp){
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while(left < right){
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auto real_right = right-1;
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auto pivot = qs_partition(left, real_right, cmp);
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quicksort(left, pivot, cmp);
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left = ++pivot;
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}
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}
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}
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#endif
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