87 lines
2.1 KiB
C++
87 lines
2.1 KiB
C++
#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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