General purpose merge sort implementation in C++11

merge.cpp

#include <iostream>
#include <vector>

using namespace std;

template <typename T>
void _Merge(vector<T> &a, int low, int mid, int high)
{
	int n, p, q,
		l = mid - low + 1,
		r = high - mid;
	auto v = a.begin();

	vector<T> left (v + low, v + mid + 1),
			  right (v + mid + 1, v + high + 1);

	for(n = low, p = q = 0; p < l && q < r; n++)
		a[n] = left[p] < right[q] ? left[p++] : right[q++];

	while(p < l)
		a[n++] = left[p++];

	while(q < r)
		a[n++] = right[q++];
}

template <typename T>
void _Sort(vector<T> &a, int low, int high)
{
	if(low + 1 > high) return;

	int mid = (low + high) / 2;
	_Sort(a, low, mid);
	_Sort(a, mid + 1, high);
	_Merge(a, low, mid, high);
}

int main()
{
	vector<int> a = {38, 27, 43, 3, 9, 82, 10};
	int n = a.size();

	_Sort(a, 0, n - 1);

	for(int i = 0; i < n; i++)
		cout << a[i] << ",\n"[i == n - 1];

	return 0;
}