Binary-Tree-Level-Order-Traversal

package com.tree.traversal.iterative;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

public class LevelOrderTraversal {
	static List<Integer> result;

	public static void main(String[] args) {
		TreeNode left = new TreeNode(2);
		TreeNode right = new TreeNode(3);
		TreeNode root = new TreeNode(1, left, right);
		left.right = new TreeNode(4, new TreeNode(6), new TreeNode(7));
		right.left = new TreeNode(5, null, new TreeNode(8));

		result = new ArrayList<Integer>();
		System.out.println("Level Order Traversal : " + levelOrderTraversal(root));
	}

	private static List<Integer> levelOrderTraversal(TreeNode root) {
		Queue<TreeNode> queue = new LinkedList<>();
		queue.add(root);
		while(!queue.isEmpty()) {
			int size = queue.size();
			while(size-- > 0) {
				TreeNode current = queue.remove();
				result.add(current.val);
				if(current.left!=null) queue.add(current.left);
				if(current.right != null) queue.add(current.right);
			}
		}
		return result;
	}
}

class TreeNode {
	int val;
	TreeNode left;
	TreeNode right;

	TreeNode() {
	}

	TreeNode(int val) {
		this.val = val;
	}

	TreeNode(int val, TreeNode left, TreeNode right) {
		this.val = val;
		this.left = left;
		this.right = right;
	}
}