traversal on Binary Tree
Last updated: March 4, 2026
Quick Overview
Perform a traversal on a binary tree and return the result.
Robinhood
March 4, 20265
11
1,176 solved
Perform a traversal on a binary tree and return the result.
This coding problem is frequently asked during Phone Screen at Robinhood. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Robinhood 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 optimize the space complexity of your solution?
- How would you parallelize this solution?
- What if the input doesn't fit in memory?
- What happens if the input contains duplicates?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to perform a traversal on a binary tree. The suitable pattern here is Depth-First Search (DFS), which is commonly used to traverse trees. DFS can be implemented using recursion...
Approach
We will implement a recursive approach for the traversal. Here are the steps:
- Define a function
traverse(node), which takes a node as its argument. - If the node is null, return an empty list (b...
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