Merge Three Sorted graphs
Last updated: May 9, 2026
Quick Overview
Given two sorted grids, merge them into a single sorted result.
Elastic
May 9, 20264
9
1,487 solved
Given two sorted grids, merge them into a single sorted result.
This coding problem is frequently asked during Phone Screen at Elastic. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Elastic 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?
- Can you solve this iteratively instead of recursively (or vice versa)?
- 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
To merge two sorted grids into a single sorted result, we can recognize that this problem exhibits a pattern similar to the 'merge' process in the merge sort algorithm. This is a natural fit for the t...
Approach
- Initialization: Create two pointers,
iandj, initialized to 0 to track the current position in each of the two grids. - Result Storage: Create an empty list
resultto store the merg...
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