gplib/include/gp/algorithms/sort.hpp

#pragma once
#include <gp/algorithms/move.hpp>
#include <gp/algorithms/partition.hpp>

namespace gp {

    namespace __details {
        template<typename it_t, typename pred>
        void selection_sort(it_t first, it_t last, pred predicate = pred{}) {
            
            while(first != last) {
                it_t traveler = first;
                it_t it = first;
                it++;
                for(;it!=last;it++) {
                    if(predicate(*it, *traveler)) traveler = it;
                }
                gp::swap(*first, *traveler);
                first++;
            }
        }

        template<typename it_t, typename pred>
        bool sort2(auto it0, auto it1, pred predicate = pred{}){
            if(it0 != it1 && predicate(*it1, *it0)) {
                gp::swap(*it0, *it1);
                return true;
            }
            return false;
        };
        /*
        template<typename it_t, typename pred>
        void quick_sort(it_t first, it_t last, pred predicate = pred{}) {
            using __details::sort2;
            if(last - first <= 2) {
                auto nit = first + (size_t)(last == first + 1);
                __details::sort2<it_t>(first, nit, predicate);
                return;
            }
            auto pivot_v = *(first + (last - first)/2);
            auto pivot = gp::partition(first, last, [&](auto& a) -> bool{
                return predicate(a, pivot_v);
            });
            gp::__details::quick_sort(first, pivot, predicate);
            gp::__details::quick_sort(pivot, last, predicate);
        }
        */
        template<typename it_t, typename pred>
        void bubble_sort(it_t first, it_t last, pred predicate = pred{}) {
            if(last - first <= 2) {
                auto nit = first + (size_t)(last == first + 1);
                __details::sort2<it_t>(first, nit, predicate);
                return;
            }
            size_t swaps;
            do {
                swaps = 0;
                auto it = first; 
                auto nit = it + 1;
                for(;;) {
                    swaps += __details::sort2<it_t>(it, nit, predicate);
                    ++it; ++nit;
                    if(nit == last) break;
                }
            } while(swaps);
        }
    }

    
    template<typename it_t, typename pred>
    void sort(it_t first, it_t last, pred predicate = pred{}) {
        return gp::__details::selection_sort(first, last, predicate);
    }
}