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Grokking the Coding Interview Patterns in JavaScript

Solution: Binary Tree Level Order Traversal

Explore how to implement level order traversal on binary trees with breadth-first search. Learn two queue-based methods to process nodes level by level, understand time and space complexities, and return a correctly formatted traversal string. This lesson helps you master BFS traversal patterns for coding interviews.

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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

Solution

So far, you’ve probably brainstormed some approaches and have an idea of how to solve this problem. Let’s explore some of these approaches and figure out which one to follow based on considerations such as time complexity and any implementation constraints.

Naive approach

The naive approach would be to first calculate the height of the tree and then recursively traverse it, level by level. The printing function would be called for every level in the range [1,he ...