2002-c-四-4

void swap(int &in1, int &in2)
{
	int tmp = in1;
	in1 = in2;
	in2 = tmp;
}

int qsort_partition(int A[], int q, int r)
{
	int i, j, k = A[r];
	for (i = q, j = q-1; i < r; i++) {
		if (A[i] < k) {
			swap(A[++j], A[i]);
		}
	}
	swap(A[++j], A[r]);
	return j;
}

void qsort(int A[], int N)
{
	if (A && N > 0) {
		stack<int> stk;
		stk.push(0);
		stk.push(N-1);
		while (!stk.empty()) {
			int l, r;
			r = stk.top();
			stk.pop();
			l = stk.top();
			stk.pop();
			if (l < r) {
				int idx = qsort_partition(A, l, r);
				stk.push(l);
				stk.push(idx-1);
				stk.push(idx+1);
				stk.push(r);
			}
		}
	}
}