PostOrder.java

/*Problem Statement: Binary Tree Postorder Traversal
Objective:
Complete the function postOrder in the editor below, which takes a parameter: a pointer to the root of a binary tree. It must print the values in the tree's postorder traversal as a single line of space-separated values.

Input Format:
Our test code passes the root node of a binary tree to the postOrder function.

Output Format:
Print the tree's postorder traversal as a single line of space-separated values.
*/

import java.util.*;
import java.io.*;

class Node {
 Node left;
 Node right;
 int data;
 
 Node(int data) {
 this.data = data;
 left = null;
 right = null;
 }
}

class PostOrder {

/* you only have to complete the function given below. 
Node is defined as 

class Node {
 int data;
 Node left;
 Node right;
}

*/

 public static void postOrder(Node root) 
 {
 if(root == null)
 {
 return;
 }
 
 postOrder(root.left);
 postOrder(root.right);
 
 System.out.print(root.data + " ");
 }

	public static Node insert(Node root, int data) {
 if(root == null) {
 return new Node(data);
 } else {
 Node cur;
 if(data <= root.data) {
 cur = insert(root.left, data);
 root.left = cur;
 } else {
 cur = insert(root.right, data);
 root.right = cur;
 }
 return root;
 }
 }

 public static void main(String[] args) {
 Scanner scan = new Scanner(System.in);
 int t = scan.nextInt();
 Node root = null;
 while(t-- > 0) {
 int data = scan.nextInt();
 root = insert(root, data);
 }
 scan.close();
 postOrder(root);
 }	
}