Merge K Sorted graphs
Last updated: February 3, 2026
Quick Overview
Given two sorted grids, merge them into a single sorted result.
Dropbox
Coding & Algorithms
Software Engineer
Dropbox
February 3, 2026Software Engineer
Onsite
Coding & Algorithms
Hard
14
11
1,309 solved
Given two sorted grids, merge them into a single sorted result.
Coding interviews at Dropbox 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
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
Key Topics to Cover
Data structure selection and trade-offs
Dynamic programming and memoization
Tree structures and recursion
Sorting and searching
Edge cases and input validation
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?
- What is the worst-case input for your solution?
- What happens if the input contains duplicates?
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Problem Analysis
To merge two sorted grids, we can utilize a min-heap (or priority queue) to efficiently merge the elements. The key pattern here is that we are dealing with two sorted data structures (the grids), and...
Approach
- Initialize a min-heap.
- Add the first element from each grid to the min-heap along with its coordinates (i, j).
- Create a result array to store the merged elements.
- While the heap is not emp...
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