Merge Three Sorted grids
Last updated: February 27, 2026
Quick Overview
Given two sorted linked lists, merge them into a single sorted result.
Twitter/X
Coding & Algorithms
Software Engineer
Twitter/X
February 27, 2026Software Engineer
Technical Screen
Coding & Algorithms
Medium
114
9
1,620 solved
Given two sorted linked lists, merge them into a single sorted result.
Twitter/X uses this problem in the Technical Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
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
Data structure selection and trade-offs
Hash maps and frequency counting
Time and space complexity analysis
Common algorithm patterns (sliding window, two pointers, BFS/DFS)
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 your solution change if the input was sorted?
- How would you modify your solution to handle streaming input?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to merge three sorted grids into a single sorted result. The key pattern here is the multi-way merge, which is commonly solved using a min-heap (or priority queue). Thi...
Approach
- Initialization: Create a min-heap to store the elements from the three grids along with their coordinates (grid index, row index, column index).
- Heap Population: Insert the first elemen...
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