function swap(arr, i, j) {
const quickSort = (arr) => {
const stack = [0, arr.length - 1];
while (stack.length > 0) {
const left = stack.pop();
const right = stack.pop();
while (i < j && arr[j] >= p) {
while (i < j && arr[i] <= p) {
if (i !== j && arr[i] !== arr[j]) {
stack.push(i + 1, right);
let arr = [3, 7, 8, 5, 2, 1, 9, 5, 4];
quickSort(arr, 0, arr.length - 1); // [1, 2, 3, 4, 5, 5, 7, 8, 9]