traversal on Binary Tree
Last updated: September 23, 2025
Quick Overview
Given a binary tree, implement a function to perform an in-order traversal and return the values of the nodes in an array. The function should take the root of the binary tree as input and output an array containing the values in the order they were visited.
Meta
September 23, 20258
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Given a binary tree, implement a function to perform an in-order traversal and return the values of the nodes in an array. The function should take the root of the binary tree as input and output an array containing the values in the order they were visited.
Meta uses this problem in the Phone Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you test this solution thoroughly?
- What is the worst-case input for your solution?
- How would you parallelize this solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to perform an in-order traversal of a binary tree, which visits nodes in the following order: left subtree, current node, right subtree. This traversal pattern is a specific in...
Approach
To implement in-order traversal, we can use a recursive approach. Here's a step-by-step breakdown:
- Base Case: If the current node is
None, return immediately as there are no nodes to visit. ...
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