Detect palindrome in matrix
Last updated: March 23, 2026
Quick Overview
Given a 2D matrix of characters, write a function to detect all occurrences of palindromic sequences in the matrix. A palindrome is defined as a sequence that reads the same forwards and backwards, and can be found in horizontal, vertical, or diagonal directions. The function should return a list of starting coordinates for each detected palindrome along with its length.
xAI
March 23, 202625
16
3,289 solved
Given a 2D matrix of characters, write a function to detect all occurrences of palindromic sequences in the matrix. A palindrome is defined as a sequence that reads the same forwards and backwards, and can be found in horizontal, vertical, or diagonal directions. The function should return a list of starting coordinates for each detected palindrome along with its length.
xAI 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
- 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?
- What happens if the input contains duplicates?
- Can you optimize the space complexity of your solution?
- Can you solve this in a single pass?
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Practice DSA ProblemsSample Answer
Problem Analysis
To detect all occurrences of palindromic sequences in a 2D matrix of characters, we can identify that this problem involves exploring multiple directions (horizontal, vertical, and diagonal). The appr...
Approach
- Iterate through each cell in the matrix as a potential starting point for a palindrome.
- Define directions to explore: horizontal (right), vertical (down), and two diagonal directions (do...
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