traversal on Binary Tree
Last updated: January 9, 2026
Quick Overview
Given a binary tree, implement a function to traverse the tree in a specified order (e.g., in-order, pre-order, or post-order) and return the values of the nodes as a list. The function should take the root node of the binary tree as input and output a list of node values in the order they were visited.
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January 9, 2026277
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Given a binary tree, implement a function to traverse the tree in a specified order (e.g., in-order, pre-order, or post-order) and return the values of the nodes as a list. The function should take the root node of the binary tree as input and output a list of node values in the order they were visited.
Coding interviews at Postmates 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
- 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 parallelize this solution?
- What if the input doesn't fit in memory?
- Can you solve this in a single pass?
- How would your solution change if the input was sorted?
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Practice DSA ProblemsSample Answer
Problem Analysis
To solve the problem of traversing a binary tree in a specified order (in-order, pre-order, or post-order), we will utilize a recursive approach. The recursive nature of tree traversal aligns well wit...
Approach
We will implement a recursive function to perform pre-order traversal:
- Base Case: If the current node is
None, return an empty list. - Process Current Node: Add the value of the current ...
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