Merge Sort

size_t
merge(vector<int>& v, vector<int>& tempVec, size_t begin, size_t mid, size_t end)
{
    size_t numCompares = 0;
    size_t split = mid - 1;
    size_t iter = begin;

    // Main loop
    while (begin <= split && mid <= end )
    {
        if (v[begin] <= v[mid])
        {
            tempVec[iter] = v[begin];
            ++begin;
        }
        else
        {
            tempVec[iter] = v[mid];
            ++mid;
        }
        ++iter;
        ++numCompares;
    }
    while (begin <= split) // Copy rest of first half
    {
        tempVec[iter] = v[begin];
        ++iter;
        ++begin;
    }
    while (mid <= end) // Copy rest of right half
    {
        tempVec[iter] = v[mid];
        ++mid;
        ++iter;
    }
    // Copy tmpArray back
    for (int i = 0; i < v.size (); ++i, --end)
    {
        v[end] = tempVec[end];
    }
    printVector (v, 0, v.size ());
    return numCompares;
}

size_t
mergeHelper (vector<int>& v, vector<int>& tempVec, size_t begin, size_t end)
{

  if (begin < end)
  {
    size_t mid = (begin + end) / 2;
    mergeHelper (v, tempVec, begin, mid);
    mergeHelper (v, tempVec, mid + 1, end);
    return merge (v, tempVec, begin, mid + 1, end);
  }
}

size_t
mergeSort (vector<int>& v)
{
    vector<int> tempVec (v.size ());
    return mergeHelper (v, tempVec, 0, v.size () - 1);
}