#ifndef MERGESORT
#define MERGESORT

#include <vector>
#include <iostream>

template <typename T>
void Split(const std::vector<T> & src, std::vector<T> & a, std::vector<T> & b){
    size_t i;

    size_t mid = src.size() / 2;

    for(i = 0; i < mid; i++) {
        a.push_back(src[i]);
    }

    for(i = mid; i < src.size(); i++) {
        b.push_back(src[i]);
    }

    return;
}

template <typename T> 
void Merge(std::vector<T> & src, 
           const std::vector<T> & a, const std::vector<T> & b){
    size_t apos{0},
        bpos{0},
        spos{0};

    while (apos < a.size() and bpos < b.size() )  {
        if (a[apos] < b[bpos]) {
           src[spos++] = a[apos++];
        } else {
           src[spos++] = b[bpos++];
        }
    }

    while ( apos < a.size()) {
       src[spos++] = a[apos++];
    }

    while ( bpos < b.size()) {
       src[spos++] = b[bpos++];
    }

    return;
}

template <typename T> 
void MergeSort(std::vector<T> &  src) {
    std::vector<T> a, b;

    if (src.size() > 1) {
        Split(src, a, b);
        MergeSort(a);
        MergeSort(b);
        Merge(src, a,b);
    }
    return;
}

#endif