Iterative (non-recursive) Quick Sort

#include <iostream>
#include <stack>
#include <utility>
using namespace std;

void quickSort(int A[], int n) {
	stack<pair<int, int>> stk;
	stk.push(make_pair(0, n-1));
	while (!stk.empty()) {
		pair<int, int> p = stk.top();
		stk.pop();
		int r = rand() % (p.second-p.first+1) + p.first;
		swap(A[r], A[p.first]);
		int j = p.first;
		for (int i=p.first+1; i<=p.second; ++i) {
			if (A[i] < A[p.first]) swap(A[++j], A[i]);
		}
		swap(A[p.first], A[j]);
		if (j-1 > p.first) stk.push(make_pair(p.first, j-1));
		if (j+1 < p.second) stk.push(make_pair(j+1, p.second));
	}
}

int main() {
	int A[8] = {4, 3, 5, 2, 1, 3, 2, 3};
	quickSort(A, 8);
	for (int i=0; i<8; ++i) cout<<A[i]<<" ";
	return 0;
}