traversal on Binary Tree
Last updated: January 13, 2026
Quick Overview
Given a binary tree, implement a function to perform an in-order traversal 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 values of the nodes visited in in-order sequence.
Neon
January 13, 20260
3
1,728 solved
Given a binary tree, implement a function to perform an in-order traversal 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 values of the nodes visited in in-order sequence.
This coding problem is frequently asked during Phone Screen at Neon. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Neon expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
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 modify your solution to handle streaming input?
- Can you optimize the space complexity of your solution?
- What if the input doesn't fit in memory?
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Problem Analysis
To perform an in-order traversal of a binary tree, we need to visit the left subtree, then the current node, and finally the right subtree. This pattern aligns with depth-first search (DFS) since we a...
Approach
- Start at the root node of the binary tree.
- If the current node is not null, recursively traverse the left subtree.
- Add the value of the current node to the output list.
- Finally, recu...
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