Detect palindrome in matrix
Last updated: February 27, 2026
Quick Overview
Given a 2D matrix of characters, write a function to detect all occurrences of palindromic sequences in the matrix. A palindromic sequence is defined as a sequence of characters that reads the same forwards and backwards, and can be found in any row, column, or diagonal of the matrix. The function should return a list of all unique palindromic sequences found, along with their starting coordinates.
Brex
February 27, 202610
12
3,717 solved
Given a 2D matrix of characters, write a function to detect all occurrences of palindromic sequences in the matrix. A palindromic sequence is defined as a sequence of characters that reads the same forwards and backwards, and can be found in any row, column, or diagonal of the matrix. The function should return a list of all unique palindromic sequences found, along with their starting coordinates.
This coding problem is frequently asked during Technical Screen at Brex. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Brex expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
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 parallelize this solution?
- Can you optimize the space complexity of your solution?
- How would you test this solution thoroughly?
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Problem Analysis
To solve the problem of detecting palindromic sequences in a 2D matrix, we can utilize the concept of searching in multiple directions: horizontally (rows), vertically (columns), and diagonally (both ...
Approach
Here’s the step-by-step algorithm to identify palindromic sequences:
- Initialize a set to store unique palindromic sequences along with their starting coordinates.
- **Iterate through each cell...
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