compression on Binary Tree
Last updated: April 9, 2026
Quick Overview
Given a binary tree, implement a function to compress the tree into a more space-efficient representation by removing all nodes that have only one child. The function should return a new binary tree that maintains the same structure but eliminates unnecessary nodes, ensuring that each node retains its original connections to its children.
Amazon
April 9, 202613
8
4,746 solved
Given a binary tree, implement a function to compress the tree into a more space-efficient representation by removing all nodes that have only one child. The function should return a new binary tree that maintains the same structure but eliminates unnecessary nodes, ensuring that each node retains its original connections to its children.
This coding problem is frequently asked during Phone Screen at Amazon. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Amazon 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 test this solution thoroughly?
- How would you parallelize this solution?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem involves compressing a binary tree by removing nodes that have only one child. This is a classic case for Depth-First Search (DFS) or recursion. The DFS approach allows us to traverse the ...
Approach
- We will implement a recursive DFS function that visits each node in the tree.
- At each node, we will check:
- If it has both left and right children, we keep the node and proceed with the recu...
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