Find cycle in matrix
Last updated: October 2, 2025
Quick Overview
Given a 2D matrix filled with integers, determine if there exists a cycle in the matrix where you can move in four possible directions (up, down, left, right) and return to the starting point. A cycle is defined as a path that starts and ends at the same cell without revisiting any cell in between. The function should return true if a cycle exists, and false otherwise.
Stripe
October 2, 2025236
4
4,663 solved
Given a 2D matrix filled with integers, determine if there exists a cycle in the matrix where you can move in four possible directions (up, down, left, right) and return to the starting point. A cycle is defined as a path that starts and ends at the same cell without revisiting any cell in between. The function should return true if a cycle exists, and false otherwise.
Coding interviews at Stripe focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
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
- Can you solve this iteratively instead of recursively (or vice versa)?
- Can you optimize the space complexity of your solution?
- How would your solution change if the input was sorted?
- How would you parallelize this solution?
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Problem Analysis
To determine if there exists a cycle in a 2D matrix, we can leverage the Depth-First Search (DFS) algorithm with backtracking. The cycle is defined as a path that starts and ends at the same cell with...
Approach
- Initialization: Create a
visitedmatrix of the same size as the input matrix to keep track of cells that have been visited in the current path. - DFS Function: Implement a recursive func...
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