Count connected components in graph
Last updated: July 21, 2025
Quick Overview
Given an undirected graph represented as an adjacency list, write a function to count the number of connected components in the graph. The function should take the number of nodes and the adjacency list as input and return the count of connected components as output.
Zscaler
July 21, 2025290
6
1,521 solved
Given an undirected graph represented as an adjacency list, write a function to count the number of connected components in the graph. The function should take the number of nodes and the adjacency list as input and return the count of connected components as output.
This coding problem is frequently asked during Take-home Project at Zscaler. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Zscaler expects candidates to write production-quality code, not just solve the puzzle.
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 your solution change if the input was sorted?
- What if the input doesn't fit in memory?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
This problem involves counting the number of connected components in an undirected graph represented as an adjacency list. The natural choice for traversing graphs is either Depth-First Search (DFS) o...
Approach
- Initialize a
visitedset to keep track of visited nodes. - Initialize a
component_countvariable to 0, which will hold the number of connected components. - Iterate through each node in t...
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