Validate matrix sorted
Last updated: October 2, 2025
Quick Overview
Given a 2D matrix, write a function to determine if each row and each column 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.
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Given a 2D matrix, write a function to determine if each row and each column 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.
This coding problem is frequently asked during Onsite at Pinterest. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Pinterest 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?
- How would you parallelize this solution?
- What if the input doesn't fit in memory?
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Practice DSA ProblemsSample Answer
Problem Analysis
To determine if each row and each column of a 2D matrix is sorted in non-decreasing order, we can observe that the problem can be approached using a straightforward iteration method. The specific patt...
Approach
- First, check each row to ensure that the elements are in non-decreasing order. For each row, iterate through the elements, comparing each element with the next one. If any element is greater than t...
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