Detect permutation in matrix
Last updated: April 25, 2026
Quick Overview
Given a matrix of integers, determine if any of its rows or columns contain a permutation of a specified target array. The function should return true if a permutation exists and false otherwise. The input will consist of the matrix dimensions, the matrix itself, and the target array, while the output should be a boolean value indicating the presence of the permutation.
SpaceX
April 25, 202625
11
4,334 solved
Given a matrix of integers, determine if any of its rows or columns contain a permutation of a specified target array. The function should return true if a permutation exists and false otherwise. The input will consist of the matrix dimensions, the matrix itself, and the target array, while the output should be a boolean value indicating the presence of the permutation.
This coding problem is frequently asked during Take-home Project at SpaceX. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. SpaceX 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
- Can you optimize the space complexity of your solution?
- What happens if the input contains duplicates?
- How would you modify your solution to handle streaming input?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to determine if any row or column in a given matrix contains a permutation of a specified target array. A permutation means that the elements of the target array can appear in ...
Approach
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Count Target Elements: First, we will create a frequency dictionary (or hashmap) of the target array elements.
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Check Rows: For each row in the matrix, we will create a frequency diction...
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