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Grokking the Coding Interview Patterns in JavaScript

Binary Tree Level Order Traversal

Explore how to perform a binary tree level order traversal using breadth-first search. This lesson helps you understand the traversal process, handle edge cases like empty trees, and implement the solution efficiently. You'll gain skills to return node values level by level, which is essential for many coding interviews.

We'll cover the following...

Statement

Given the root of a binary tree, display the values of its nodes while performing a level order traversal. Return the node values for all levels in a string separated by the character :. If the tree is empty, i.e., the number of nodes is 00, then return “None” as the output.

Constraints:

  • The number of nodes in the tree is in the range [0,500][0, 500].

  • −103≤-10^3 \leq Node.data ≤103\leq 10^3

Examples

Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

Technical Quiz
1.

How does BFS ensure that it visits all nodes in a binary tree while traversing level by level?

A.

By using a stack data structure to keep track of visited nodes

B.

By using a queue data structure to maintain the order of node exploration

C.

By recursively traversing the left and right subtrees in a depth-first manner

D.

By randomizing the order of node exploration for better coverage

1 / 3

Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3
4
5

Try it yourself

Implement your solution in main.js in the following coding playground. You’ll need the provided supporting code to implement your solution.

Note: The binary tree node’s class has members left and right to store references to other nodes, along with the member data to hold the node’s value.

JavaScript
usercode > main.js
// Definition of a binary tree node

// class TreeNode {

//   constructor(data) {

//     this.data = data;

//     this.left = null;

//     this.right = null;

//   }

// }



import {TreeNode} from './ds_v1/BinaryTree.js';

import Queue from "./queue.js";





export let  levelOrderTraversal = function(root) {



    // Replace this placeholder return statement with your code

    return ""

}
Binary Tree Level Order Traversal