compression on Binary Tree
Last updated: October 4, 2025
Quick Overview
Given a binary tree, implement a function to compress the tree into a more compact representation by removing all nodes with a value of zero and adjusting the tree structure accordingly. The output should be the root of the new compressed binary tree.
Jane Street
October 4, 202537
12
1,800 solved
Given a binary tree, implement a function to compress the tree into a more compact representation by removing all nodes with a value of zero and adjusting the tree structure accordingly. The output should be the root of the new compressed binary tree.
Jane Street uses this problem in the Phone Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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?
- What if the input doesn't fit in memory?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to compress a binary tree by removing all nodes with a value of zero and adjusting the tree structure accordingly. This problem is well-suited for a **Depth-First Search (DFS)*...
Approach
We will use a recursive DFS function to traverse the binary tree. The main steps are as follows:
- Base Case: If the current node is null, return null.
- Recursive Case: Recursively call the...
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