Coding Challenge Day-13: Problem 1: Level-order traversal of a Binary tree

Hello! So I’m doing a 100 day coding challenge where I solve a few questions every day and thought of posting them here on my blog so that you guys can join the challenge too!

Welcome to Coding challenge Day 13: Problem 1! Be sure to post your answers, queries etc in the comments!

Problem: Level-order traversal of a Binary tree

Sample:

Output:

Level: 0
1
Level: 1
2
3
Level: 2
4
5
6
7
Level: 3

Solution:

package tree.binarytree;

import java.util.Queue;
import java.util.LinkedList;

public class Program011level_order_traversal {
	
	static class Node{
		int data;
		Node left, right;
		
		public Node(int d){
			data=d;
			left=right=null;
		}
	}
	
	static class Binary_tree{
		Node root;
		
		public Binary_tree(){
			root=null;
		}
		
		public void add_left (Node parent_node, Node node){
			parent_node.left= node;
		}
		
		public void add_right (Node parent_node, Node node){	
			parent_node.right= node;
		}
		
		public void level_order_traversal(){
			Node node= root;
			Node level_node= new Node(-1);
			Node previous_node= root;
			int level=0;
			
			Queue<Node> queue= new LinkedList<Node>();
			queue.add(root);
			queue.add(level_node);
			
			System.out.println("Level: 0");
			
			while(!queue.isEmpty()){
				Node front_node= queue.poll();
				if(front_node.data==-1){
					level++;
					if(previous_node.data!=-1){
						queue.add(level_node);
						System.out.println("Level: " + level);
					}
				} else{
					System.out.println(front_node.data);
					if(front_node.left!=null){
						queue.add(front_node.left);
					}
					
					if(front_node.right!=null){
						queue.add(front_node.right);
					}
				}
				
				previous_node= front_node;
			}
		}
		
	}
	
	
	public static void main (String [] args){
		Binary_tree tree= new Binary_tree();
		
		tree.root= new Node(1);
		
		Node node2= new Node(2);
		tree.add_left(tree.root, node2);
		
		Node node3= new Node(3);
		tree.add_right(tree.root, node3);
		
		Node node4= new Node (4);
		tree.add_left(node2, node4);
		
		Node node5= new Node(5);
		tree.add_right(node2, node5);
		
		Node node6= new Node(6);
		tree.add_left(node3, node6);
		
		Node node7= new Node(7);
		tree.add_right(node3, node7);
		
		tree.level_order_traversal();
	}
}
		

Download Code

Happy Learning!!