Validate matrix sorted
Last updated: October 6, 2025
Quick Overview
Given a 2D matrix, write a function to determine if each row and each column of the matrix is sorted in non-decreasing order. The function should take the matrix as input and return a boolean value indicating whether the matrix is sorted according to these criteria.
Square/Block
October 6, 202591
12
2,423 solved
Given a 2D matrix, write a function to determine if each row and each column of the matrix is sorted in non-decreasing order. The function should take the matrix as input and return a boolean value indicating whether the matrix is sorted according to these criteria.
Square/Block uses this problem in the Onsite 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
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 test this solution thoroughly?
- What if the input doesn't fit in memory?
- How would you parallelize this solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to validate whether each row and each column of a given 2D matrix is sorted in non-decreasing order. This can be approached using a simple linear scan for each row and column. ...
Approach
- Iterate through each row: For each row in the matrix, compare each element with the next one to ensure they are in non-decreasing order. If any two adjacent elements fail this check, return Fal...
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