Find connected components in matrix
Last updated: December 22, 2025
Quick Overview
Given a binary matrix consisting of 0s and 1s, write a function to find all connected components of 1s, where connectivity is defined as horizontal or vertical adjacency. The function should return a list of lists, where each inner list contains the coordinates of the cells that form a connected component.
Airbnb
December 22, 202518
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3,964 solved
Given a binary matrix consisting of 0s and 1s, write a function to find all connected components of 1s, where connectivity is defined as horizontal or vertical adjacency. The function should return a list of lists, where each inner list contains the coordinates of the cells that form a connected component.
Coding interviews at Airbnb 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
- 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
- What happens if the input contains duplicates?
- How would you parallelize this solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To solve the problem of finding connected components in a binary matrix, we can recognize that it resembles a graph traversal problem, where each '1' represents a node and the connectivity (horizontal...
Approach
- Initialize a results list: This will store all the connected components found.
- Iterate through each cell in the matrix: For each '1' found, initiate a DFS from that cell to explore its...
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