Validate matrix complete
Last updated: May 22, 2026
Quick Overview
Given a 2D matrix, write a function to validate whether the matrix is complete, meaning that every row and every column contains all integers from 1 to n, where n is the size of the matrix. The function should return true if the matrix is complete and false otherwise.
DoorDash
May 22, 2026256
13
2,332 solved
Given a 2D matrix, write a function to validate whether the matrix is complete, meaning that every row and every column contains all integers from 1 to n, where n is the size of the matrix. The function should return true if the matrix is complete and false otherwise.
DoorDash uses this problem in the Phone Screen 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 you modify your solution to handle streaming input?
- What if the input doesn't fit in memory?
- Can you solve this in a single pass?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to validate whether a given 2D matrix is 'complete', meaning every row and every column contains all integers from 1 to n, where n is the size of the matrix. The specific patte...
Approach
- First, check if the matrix is empty or if the number of rows does not match the number of columns (i.e., it is not n x n). If so, return false.
- Create two sets: one for tracking numbers in each ...
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