c++ implementation for quick-sort algorithm

quick_sort.cpp

void quickSort(int *a, int l, int r) {
	if (l >= r) return;
	// this is a good coding style to avoid overflow
	int mid = l + (r - l) / 2;
	// choose a[mid] as pivot to speed up for sequences in order
	int pivot = a[mid];
	std::swap(a[mid], a[r]);
	int i = l, j = r - 1;
	while (i <= j) {
		while (i <= j && a[i] <= pivot) i++;
		while (i <= j && a[j] > pivot) j--;
		if (i < j) std::swap(a[i], a[j]);
	}
	std::swap(a[r], a[i]);
	quickSort(a, l, i - 1);
	quickSort(a, i + 1, r);
}