traversal on Binary Tree
Last updated: July 4, 2025
Quick Overview
Given a binary tree, implement a function to perform a traversal (in-order, pre-order, or post-order) and return the values of the nodes in a list. The function should take the root node of the binary tree as input and output a list of node values in the specified traversal order.
Zillow
July 4, 20250
13
94 solved
Given a binary tree, implement a function to perform a traversal (in-order, pre-order, or post-order) and return the values of the nodes in a list. The function should take the root node of the binary tree as input and output a list of node values in the specified traversal order.
Zillow uses this problem in the Onsite 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
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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
- What is the worst-case input for your solution?
- Can you solve this in a single pass?
- How would you test this solution thoroughly?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Problem Analysis
The problem requires performing a traversal on a binary tree, which can be approached using Depth-First Search (DFS) techniques. Specifically, in-order, pre-order, or post-order traversals can be util...
Approach
- Choose the Traversal Type: Identify which traversal (in-order, pre-order, post-order) is needed. For example, in-order traversal visits the left subtree first, then the node, and finally the ri...
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