compression on Binary Tree
Last updated: January 25, 2026
Quick Overview
Given a binary tree, implement a function to compress the tree into a more space-efficient representation. The output should be a serialized string that captures the structure and values of the tree, allowing for reconstruction of the original tree. The function should handle edge cases, such as empty trees, and ensure that the serialization is both compact and unambiguous.
xAI
January 25, 202683
8
2,046 solved
Given a binary tree, implement a function to compress the tree into a more space-efficient representation. The output should be a serialized string that captures the structure and values of the tree, allowing for reconstruction of the original tree. The function should handle edge cases, such as empty trees, and ensure that the serialization is both compact and unambiguous.
This coding problem is frequently asked during Technical Screen at xAI. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. xAI 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
- What happens if the input contains duplicates?
- What is the worst-case input for your solution?
- How would you parallelize this solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires compressing a binary tree into a serialized string format that can be easily reconstructed later. This problem can be approached using a Depth-First Search (DFS) traversal pattern...
Approach
- Base Case: If the current node is
None, append a special character (e.g., 'X') to represent a null node. - Process Node: When visiting a node, append its value to the result string.
- *...
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