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