Validate matrix sorted
Last updated: June 10, 2026
Quick Overview
Given a 2D matrix of integers, write a function to determine if each row and each column is sorted in non-decreasing order. The function should return a boolean value: true if the matrix is sorted, and false otherwise.
Stripe
June 10, 202610
8
4,224 solved
Given a 2D matrix of integers, write a function to determine if each row and each column is sorted in non-decreasing order. The function should return a boolean value: true if the matrix is sorted, and false otherwise.
Coding interviews at Stripe 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
- 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?
- Can you optimize the space complexity of your solution?
- What if the input doesn't fit in memory?
- How would you parallelize this solution?
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Problem Analysis
To determine if a 2D matrix is sorted both row-wise and column-wise, we can utilize a straightforward approach with a nested loop. The specific pattern here is a simple iteration over the matrix since...
Approach
- Iterate through each row of the matrix:
- For each row, check if it is sorted by comparing each element with the next one. For example, in the row
[1, 2, 3], we check1 <= 2,2 <= 3. If an...
- For each row, check if it is sorted by comparing each element with the next one. For example, in the row
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