二路归并排序

#include <vector>
#include <iostream>
#include <algorithm>
#include <iterator>

template<typename I>
void doMerge(I begin, I midPoint, I end)
{
    typedef std::vector<typename std::iterator_traits<I>::value_type> TmpVec;

    TmpVec  tmp(std::make_move_iterator(begin), std::make_move_iterator(end));

    TmpVec::iterator   beginAlt   = std::begin(tmp);
    TmpVec::iterator   endAlt     = std::end(tmp);
    TmpVec::iterator   midAlt     = std::next(beginAlt, std::distance(begin, midPoint));


    TmpVec::iterator   l   = beginAlt;
    TmpVec::iterator   r   = midAlt;
    I                  i   = begin;

    while(l < midAlt && r < endAlt)
    {
        *i = std::move((*l < *r) ? *l++ : *r++);
        ++i;
    }
    while(l < midAlt)
    {   *i  = std::move(*l++);
        ++i;
    }
    while(r < endAlt)
    {   *i  = std::move(*r++);
        ++i;
    }
}
template<typename I>
void mergeSort(I begin, I end)
{
    std::size_t length  = std::distance(begin, end);
    if (length <= 1)
    {   return;
    }

    std::size_t mid      = length/2;
    I           midPoint = std::next(begin, mid); // ++

    mergeSort(begin, midPoint);
    mergeSort(midPoint, end);

    doMerge(begin, midPoint, end);
}


int main()
{
	int arr[] = {5,12,45,2,67,8};
	size_t count=sizeof(arr)/sizeof(int);
    std::vector<int> data(arr, arr+count);

    mergeSort(std::begin(data), std::end(data));

    std::copy(std::begin(data), std::end(data), std::ostream_iterator<int>(std::cout, ", "));
    std::cout << "\n";
}