Simplest iterative algorithm Post order traversal

package com.test;

import java.util.Stack;

public class PostOrderTraversal {

static class Node {

int data;

Node left, right;

Node(int item) {

data = item;

left = right;

}

}

private void pfIterate(Node root) {

Node prev = null;

Stack stack = new Stack<>();

stack.push(root);

while (!stack.isEmpty()) {

root = stack.pop();

if (root.left == null && root.right == null) {

System.out.print(root.data + " ");

prev = root;

} else if (prev == root.left || prev == root.right) {

System.out.print(root.data + " ");

prev = root;

} else {

stack.push(root);

if (root.right != null)

stack.push(root.right);

if (root.left != null)

stack.push(root.left);

}

}

}

public static void main(String[] args) {

// Let us create trees shown in above diagram

Node root = new Node(1);

root.left = new Node(2);

root.right = new Node(3);

root.left.left = new Node(4);

root.left.right = new Node(5);

root.right.left = new Node(6);

root.right.right = new Node(7);

new PostOrderTraversal().pfIterate(root);

}

}