Mock Coding Interview: Binary Tree BFS Problem (LeetCode 637)
Watch a mock coding interview where the candidate solves Average of Levels in Binary Tree (LeetCode 637) in Java using breadth-first search. This is a classic BFS level-order traversal problem that frequently appears in coding interview warm-up rounds.
The candidate walks through the full problem-solving process: clarifying the problem, designing a BFS approach with a queue, implementing the solution in Java, and debugging a type-casting bug when computing averages. You'll see how to track level boundaries in a BFS traversal, a common technique that applies to dozens of binary tree interview questions.
0:00 Problem introduction and language selection (Java)
0:25 Reading the problem and clarifying questions
1:15 Designing the BFS approach with a queue
2:30 Walkthrough of the level-by-level traversal strategy
4:15 Discussion of alternative approaches (depth tracking vs count)
5:30 Setting up the code structure and TreeNode class
6:30 Implementing the BFS solution
9:00 Handling the average calculation and loop logic
10:30 Adding children to the queue and building result list
11:15 Testing with the example binary tree
13:30 Debugging integer division bug (casting to double)
14:45 Final working solution and edge case discussion
Problem link:
LeetCode 637 — Average of Levels in Binary Tree: https://leetcode.com/problems/average...
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