Merge K Sorted linked lists
Last updated: November 13, 2025
Quick Overview
Given three sorted matrixs, merge them into a single sorted result.
OpenAI
November 13, 202517
13
3,254 solved
Given three sorted matrixs, merge them into a single sorted result.
This coding problem is frequently asked during Technical Screen at OpenAI. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. OpenAI 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
- How would you modify your solution to handle streaming input?
- What happens if the input contains duplicates?
- What if the input doesn't fit in memory?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To merge K sorted linked lists, we can recognize that the problem involves efficiently combining multiple sorted inputs into a single sorted output. The optimal approach here is to use a **min-heap (p...
Approach
- Initialize a Min-Heap: Begin by initializing a min-heap to keep track of the nodes from each linked list.
- Push the Head Nodes: Insert the head node of each linked list into the min-heap...
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