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    Implementing Post-Order Traversal of Binary Tree in Java
    Published on: 2018-10-27 06:10:12

    This tutorial provides code for implementing post-order traversal of a Binary Tree.

    Post-Order Traversal of Binary Tree


    Binary Tree traversal is a process of visiting each node of Binary Tree exactly once. Post-Order traversal falls into depth-first search as search is deepended on child nodes of a node before moving to its sibling.

    Post-order traversal is a special type of Tree traversal wherein left child and right child are visited before a node. This results into recursive function calls as you can't print a node data unless all of its left and right child nodes data have been printed.

    Let's consider below Binary Tree - 

    Here is the Post-Order Traversal of above tree -

    20 10 40 30 60 90 80 70 50 
    

     

    Java Implementation of Post-Order Traversal of Binary Tree


    Here is Java code for Binary Tree containing methods for inserting data and post-order traversal - 

    package com.aksain.data.structures;
    
    public class BinaryTreeWithPostOrderTraversal<T extends Comparable<T>> {
    	private Node root;
    	
    	private class Node {
    		T data;
    		Node left;
    		Node right;
    		
    		private Node(T data) {
    			this.data = data;
    		}
    	}
    	
    	private Node doInsert(T data, Node node) {
    		if(node == null) {
    			return new Node(data);
    		}
    		int result = data.compareTo(node.data);
    		if(result < 0) {
    			node.left = doInsert(data, node.left);
    		} else if(result > 0) {
    			node.right = doInsert(data, node.right);
    		}
    		
    		return node;
    	}
    	
    	public void insert(T data) {		
    		root = doInsert(data, root);
    	}
    	
    	private void doPostOrder(Node node) {
    		if(node == null) {
    			return;
    		}
    		doPostOrder(node.left);
    		doPostOrder(node.right);
    		System.out.print(node.data + " ");
    	}
    	
    	public void postOrder() {
    		doPostOrder(root);
    		System.out.println();
    	}
    	
    	public static void main(String[] args) {
    		final BinaryTreeWithPostOrderTraversal<Integer> binaryTree = new BinaryTreeWithPostOrderTraversal<>();
    		binaryTree.insert(50);
    		binaryTree.insert(30);
    		binaryTree.insert(10);
    		binaryTree.insert(20);
    		binaryTree.insert(40);
    		binaryTree.insert(70);
    		binaryTree.insert(60);
    		binaryTree.insert(80);
    		binaryTree.insert(90);
    		
    		binaryTree.postOrder();
    	}
    }
    

     

    Here is the output of above code - 

    20 10 40 30 60 90 80 70 50 
    

     

    Thank you for reading through the tutorial. In case of any feedback/questions/concerns, you can communicate same to us through your comments and we shall get back to you as soon as possible.

    Published on: 2018-10-27 06:10:12

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