traversal on Binary Tree
Last updated: October 1, 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 traversal.
DE Shaw
October 1, 20255
10
4,379 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 traversal.
Coding interviews at DE Shaw focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
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 your solution change if the input was sorted?
- How would you parallelize this solution?
- How would you test this solution thoroughly?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to perform a traversal on a binary tree, which can be accomplished using Depth-First Search (DFS) techniques. Given that we have three types of tree traversal (in-order, pre-or...
Approach
- Choose the traversal type: Let's say we choose in-order traversal for this example, which visits nodes in the order of left child, root, and then right child.
- **Define the recursive functi...
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