Merge K Sorted binary trees
Last updated: June 4, 2026
Quick Overview
Given two sorted matrixs, merge them into a single sorted result.
Square/Block
June 4, 2026234
15
253 solved
Given two sorted matrixs, merge them into a single sorted result.
This coding problem is frequently asked during Phone Screen at Square/Block. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Square/Block 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 solve this in a single pass?
- How would you test this solution thoroughly?
- What is the worst-case input for your solution?
- 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 merge two sorted matrices (representing binary trees) into a single sorted result. The key pattern that applies here is the two pointers technique, which is effective wh...
Approach
- Initialize two pointers,
iandj, starting at the beginning of each matrix. - Create an empty list called
mergedto store the merged result. - While both pointers are within the bounds ...
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