DFS on graph
Last updated: August 23, 2025
Quick Overview
Implement a Depth-First Search (DFS) algorithm to traverse a given graph represented as an adjacency list. Your function should take the graph and a starting node as input, and return a list of nodes in the order they are visited. Ensure that your solution handles cycles and avoids revisiting nodes.
NVIDIA
August 23, 20256
3
2,667 solved
Implement a Depth-First Search (DFS) algorithm to traverse a given graph represented as an adjacency list. Your function should take the graph and a starting node as input, and return a list of nodes in the order they are visited. Ensure that your solution handles cycles and avoids revisiting nodes.
NVIDIA uses this problem in the Technical Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
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
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you parallelize this solution?
- How would your solution change if the input was sorted?
- How would you test this solution thoroughly?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to implement a Depth-First Search (DFS) algorithm to traverse a graph represented as an adjacency list. The specific pattern here is DFS, which is ideal for exploring all the n...
Approach
- Initialization: Start by defining a function
dfs(graph, start)wheregraphis the adjacency list andstartis the starting node. Initialize an empty listvisitedto keep track of the or...
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