Detect palindrome in matrix
Last updated: July 14, 2025
Quick Overview
Given a 2D matrix of characters, write a function to detect all occurrences of palindromic sequences of length at least 3 in any direction (horizontally, vertically, or diagonally). The function should return a list of starting coordinates for each detected palindrome, along with the palindrome string itself. The solution should efficiently handle matrices of varying sizes and complexities.
Palo Alto Networks
July 14, 202537
12
1,571 solved
Given a 2D matrix of characters, write a function to detect all occurrences of palindromic sequences of length at least 3 in any direction (horizontally, vertically, or diagonally). The function should return a list of starting coordinates for each detected palindrome, along with the palindrome string itself. The solution should efficiently handle matrices of varying sizes and complexities.
This coding problem is frequently asked during Technical Screen at Palo Alto Networks. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Palo Alto Networks expects candidates to write production-quality code, not just solve the puzzle.
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?
- How would your solution change if the input was sorted?
- How would you parallelize this solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To detect palindromic sequences in a 2D matrix, we need to consider multiple directions: horizontally, vertically, and diagonally (both primary and secondary diagonals). The two-pointer technique can ...
Approach
- Initialization: Create a result list to store the starting coordinates and the palindrome strings.
- Iterate through each cell: For each cell in the matrix, treat it as the center of a pot...
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