105 lines
2.8 KiB
C++
105 lines
2.8 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_DETAIL_ALGORITHM_HPP
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#define REXY_DETAIL_ALGORITHM_HPP
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#include "../utility.hpp" //swap
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#include <type_traits> //nothrow_invocable
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#include <functional> //less, greater
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#include <utility> //pair
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#include <iterator> //iterator_traits
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#include <cstdlib> //size_t
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namespace rexy::detail{
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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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noexcept(std::is_nothrow_invocable<Compare,decltype(*left),decltype(*right)>::value &&
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noexcept(swap(*left,*right)))
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{
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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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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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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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swap(*left, *right);
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return left;
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}
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template<class Iter, class Op>
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constexpr std::pair<size_t,size_t> max_suffix(const Iter& needle, size_t nlen, const Op& op = Op()){
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using value_type = typename std::iterator_traits<Iter>::value_type;
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size_t max_suffix = -1;
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size_t j = 0;
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size_t k = 1;
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size_t period = 1;
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value_type a;
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value_type b;
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while(j + k < nlen){
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a = needle[j + k];
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b = needle[max_suffix + k];
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if(op(a, b)){
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j += k;
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k = 1;
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period = j - max_suffix;
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}else if(a == b){
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if(k != period){
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++k;
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}else{
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j += period;
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k = 1;
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}
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}else{
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max_suffix = j++;
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k = period = 1;
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}
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}
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return {max_suffix, period};
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}
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template<class Iter>
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constexpr std::pair<size_t,size_t> critical_factorization(const Iter& nstart, const Iter& nend){
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auto msuffix = max_suffix(nstart, nend - nstart, std::less{});
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auto msuffix_rev = max_suffix(nstart, nend - nstart, std::greater{});
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if(msuffix.first < msuffix_rev.first){
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return msuffix_rev;
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}
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return msuffix;
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}
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template<class Iter>
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constexpr bool iter_compare(const Iter& left, const Iter& right, size_t length){
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for(size_t i = 0;i < length;++i){
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if(left[i] != right[i])
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return false;
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}
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return true;
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}
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}
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#endif
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