Validate matrix sorted
Last updated: July 23, 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.
TikTok
July 23, 2025135
4
2,123 solved
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.
TikTok 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
- 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
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?
- Can you solve this in a single pass?
- What happens if the input contains duplicates?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To determine if a 2D matrix is sorted in non-decreasing order both row-wise and column-wise, we can use a straightforward approach that involves iterating through each row and each column. The specifi...
Approach
The algorithm can be broken down into the following steps:
- Check Rows: Iterate through each row of the matrix. For each row, compare each element with the next element in the row to ensure th...
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