traversal on Binary Tree
Last updated: December 20, 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 integers representing the order of node values as per the specified traversal method.
Mastercard
December 20, 20257
11
2,894 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 integers representing the order of node values as per the specified traversal method.
This coding problem is frequently asked during Take-home Project at Mastercard. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Mastercard expects candidates to write production-quality code, not just solve the puzzle.
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
- Can you solve this in a single pass?
- What happens if the input contains duplicates?
- How would you parallelize this solution?
- How would your solution change if the input was sorted?
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Problem Analysis
The problem requires traversing a binary tree using one of the traversal methods: in-order, pre-order, or post-order. The key pattern here is a Depth-First Search (DFS) approach, which is particul...
Approach
We will define a function that accepts the root node and returns a list of node values based on the specified traversal method. For example, if we choose in-order traversal, we would visit the left su...
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