Spiral/Zigzag level order traversal of binary tree in java

If you want to practice data structure and algorithm programs, you can go through data structure and algorithm interview questions.
This is 6th part of java binary tree tutorial.

In this post, we will see about Spiral/Zigzag Level Order binary tree traversal in java.

Spiral/Zigzag Level Order traversal:

 Spiral/Zigzag Level order traversal of below tree will be:


Steps for solution:
  1. Create an empty stack s and push root to it.
  2. while stack is not NULL Do following
    1. Create a empty stack called tempStack.
    2. Pop a node from stack and push it to tempStack depending on directionFlag
    3. Change directionFlag to change the direction of traversal
    4. set stack=tempStack

 
// prints in Spiral/Zigzag level order
 public static void spiralOrZigzagLevelOrder(TreeNode root) {
        if(root==null) return; 
        Stack<TreeNode> stack=new Stack<TreeNode>();
        stack.push(root);
        
        boolean directionflag=false;
        while(!stack.isEmpty())
        {
            Stack<TreeNode> tempStack=new Stack<TreeNode>();
        
            while(!stack.isEmpty())
            {
                TreeNode tempNode=stack.pop();
             System.out.printf("%d ",tempNode.data);
                if(!directionflag) 
                {
                    if(tempNode.left!=null) 
                     tempStack.push(tempNode.left);
                    if(tempNode.right!=null) 
                     tempStack.push(tempNode.right);
                }else
                {
                    if(tempNode.right!=null) 
                     tempStack.push(tempNode.right);
                    if(tempNode.left!=null) 
                     tempStack.push(tempNode.left);
                }
            }
            // for changing direction
            directionflag=!directionflag; 
      
            stack=tempStack; 
        }
     
    }

Example:
Lets say your binary tree is :


So Spiral/Zigzag Level Order traversal will work as below:

Lets create java program for Spiral/Zigzag Level traversal:
 
package org.arpit.java2blog;

import java.util.Queue;
import java.util.LinkedList;
public class BinaryTree {

 
 public static class TreeNode
 {
  int data;
  TreeNode left;
  TreeNode right;
  TreeNode(int data)
  {
   this.data=data;
  }
 }
 
// prints spiral/zigzag level order
 public static void spiralOrZigzagLevelOrder(TreeNode root) {
        if(root==null) return; 
        Stack<TreeNode> stack=new Stack<TreeNode>();
        stack.push(root);
        
        boolean directionflag=false;
        while(!stack.isEmpty())
        {
            Stack<TreeNode> tempStack=new Stack<TreeNode>();
        
            while(!stack.isEmpty())
            {
                TreeNode tempNode=stack.pop();
             System.out.printf("%d ",tempNode.data);
                if(!directionflag) 
                {
                    if(tempNode.left!=null) 
                     tempStack.push(tempNode.left);
                    if(tempNode.right!=null) 
                     tempStack.push(tempNode.right);
                }else
                {
                    if(tempNode.right!=null) 
                     tempStack.push(tempNode.right);
                    if(tempNode.left!=null) 
                     tempStack.push(tempNode.left);
                }
            }
            // for changing direction
            directionflag=!directionflag; 
      
            stack=tempStack; 
        }
     
    }
 public static void main(String[] args)
 {
  BinaryTree bi=new BinaryTree();
  // Creating a binary tree
  TreeNode rootNode=createBinaryTree();
  System.out.println("Spiral/Zigzag traversal of binary tree :");
  spiralOrZigzagLevelOrder(rootNode);
 }
 
 public static TreeNode createBinaryTree()
 {
  
  TreeNode rootNode =new TreeNode(40);
  TreeNode node20=new TreeNode(20);
  TreeNode node10=new TreeNode(10);
  TreeNode node30=new TreeNode(30);
  TreeNode node60=new TreeNode(60);
  TreeNode node50=new TreeNode(50);
  TreeNode node70=new TreeNode(70);
  TreeNode node5=new TreeNode(5);
  TreeNode node55=new TreeNode(55);
  
  rootNode.left=node20;
  rootNode.right=node60;
  
  node20.left=node10;
  node20.right=node30;
  
  node60.left=node50;
  node60.right=node70;
  node10.left=node5;
  node50.right=node55;
  
  return rootNode;
 }
}

Run above program and you will get following output:
 
Spiral/Zigzag traversal of binary tree :
40 60 20 10 30 50 70 55 5 

Java Binary tree tutorial:

    Binary tree in java Binary tree preorder traversal Binary tree postorder traversal Binary tree inorder traversal Binary tree level order traversal Binary tree spiral order traversal Binary tree reverse level order traversal Binary tree boundary traversal Print leaf nodes of binary tree Count leaf nodes in binary tree get maximum element in binary tree Print all paths from root to leaf in binary tree Print vertical sum of binary tree in java Get level of node in binary tree in java Lowest common ancestor(LCA) in binary tree in java

Please go through java interview programs for more such programs.

Written by Arpit:

If you have read the post and liked it. Please connect with me on Facebook | Twitter | Google Plus

 

Java tutorial for beginners Copyright © 2012