Count median in matrix
Last updated: November 11, 2025
Quick Overview
Given a matrix of integers, write a function to calculate the median value of all the elements in the matrix. The input will be a 2D array of integers, and the output should be a single integer representing the median. If the total number of elements is even, return the average of the two middle values as an integer.
PlanetScale
November 11, 2025291
11
2,510 solved
Given a matrix of integers, write a function to calculate the median value of all the elements in the matrix. The input will be a 2D array of integers, and the output should be a single integer representing the median. If the total number of elements is even, return the average of the two middle values as an integer.
This coding problem is frequently asked during Take-home Project at PlanetScale. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. PlanetScale 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 test this solution thoroughly?
- What if the input doesn't fit in memory?
- What is the worst-case input for your solution?
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Problem Analysis
To find the median in a matrix of integers, we need to understand how to handle sorted data efficiently. The median is defined as the middle value in a list of numbers. If the total number of elements...
Approach
- Flatten the Matrix: Convert the 2D matrix into a 1D list of integers. For example, given the matrix [[1, 3], [2]], the flattened list would be [1, 3, 2].
- Sort the Flattened List: Sort th...
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