Merge K Sorted binary trees
Last updated: May 6, 2026
Quick Overview
Given k sorted matrixs, merge them into a single sorted result.
OpenAI
Coding & Algorithms
Machine Learning Engineer
OpenAI
May 6, 2026Machine Learning Engineer
Onsite
Coding & Algorithms
Medium
10
10
933 solved
Given k sorted matrixs, merge them into a single sorted result.
Coding interviews at OpenAI 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
- 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
Dynamic programming and memoization
Tree structures and recursion
Hash maps and frequency counting
Common algorithm patterns (sliding window, two pointers, BFS/DFS)
Time and space complexity analysis
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 parallelize this solution?
- What if the input doesn't fit in memory?
- What happens if the input contains duplicates?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires merging k sorted binary trees into a single sorted result. The underlying pattern here can be seen as a variation of the 'merging k sorted lists' problem, which can be effectively...
Approach
- Initialize a min-heap: Start by inserting the root nodes of all k trees into a min-heap. The min-heap will allow us to always access the smallest available node across the trees.
- **Extract...
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