Find connected components in array
Last updated: October 13, 2025
Quick Overview
Given an undirected graph represented as an array of edges, write a function to find and return all connected components in the graph. Each connected component should be represented as a list of vertices, and the output should be a list of these components. The function should handle graphs with varying numbers of vertices and edges efficiently.
PayPal
October 13, 202521
11
2,932 solved
Given an undirected graph represented as an array of edges, write a function to find and return all connected components in the graph. Each connected component should be represented as a list of vertices, and the output should be a list of these components. The function should handle graphs with varying numbers of vertices and edges efficiently.
This coding problem is frequently asked during Phone Screen at PayPal. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. PayPal 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
- What if the input doesn't fit in memory?
- Can you solve this iteratively instead of recursively (or vice versa)?
- Can you solve this in a single pass?
- How would your solution change if the input was sorted?
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Practice DSA ProblemsSample Answer
Problem Analysis
To find connected components in an undirected graph represented by an array of edges, we can utilize Depth-First Search (DFS) or Breadth-First Search (BFS). This problem exhibits the characteristics o...
Approach
- Build the Graph: Use a dictionary to create an adjacency list representation of the graph from the edges list. For example, given edges
[(0, 1), (1, 2), (3, 4)], the adjacency list will be: `...
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