快速排序

void quick_sort(int q[], int l ,int r)
{
	if (l >= r) return;
	
	int temp = q[l + r >> 1], i = l - 1, j = r + 1;
	while (i < j)
	{
		do i ++ ; while (q[i] < temp);
		do j -- ; while (q[j] > temp);
		if (i < j) swap (q[i], q[j]);
	}
	
	quick_sort (q, l, j);
	quick_sort (q, j + 1, r);
}