DFS on linked list
Last updated: September 16, 2025
Quick Overview
Implement a Depth-First Search (DFS) algorithm to traverse a linked list. Given the head of a singly linked list, return a list of the values in the order they are visited during the DFS traversal. The output should be an array of integers representing the values of the nodes.
Visa
September 16, 202510
7
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Implement a Depth-First Search (DFS) algorithm to traverse a linked list. Given the head of a singly linked list, return a list of the values in the order they are visited during the DFS traversal. The output should be an array of integers representing the values of the nodes.
This coding problem is frequently asked during Take-home Project at Visa. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Visa 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
- What happens if the input contains duplicates?
- Can you solve this iteratively instead of recursively (or vice versa)?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
In this problem, we need to perform a Depth-First Search (DFS) traversal of a singly linked list. The linked list can be visualized as a series of nodes where each node points to the next node. The DF...
Approach
- Initialize an empty list to store the values of the nodes we visit during the DFS traversal.
- Start from the head of the list. If the head is None (i.e., the list is empty), return the e...
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