DFS on linked list
Last updated: July 14, 2025
Quick Overview
Implement a depth-first search (DFS) algorithm on a linked list to traverse the list and return the values in the order they are visited. Given the head of a singly linked list, your function should output an array containing the values of the nodes in the order they are encountered during the DFS traversal.
JPMorgan
July 14, 202556
9
2,567 solved
Implement a depth-first search (DFS) algorithm on a linked list to traverse the list and return the values in the order they are visited. Given the head of a singly linked list, your function should output an array containing the values of the nodes in the order they are encountered during the DFS traversal.
This coding problem is frequently asked during Technical Screen at JPMorgan. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. JPMorgan 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 if the input doesn't fit in memory?
- What happens if the input contains duplicates?
- How would you test this solution thoroughly?
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Problem Analysis
The problem requires us to perform a depth-first search (DFS) on a singly linked list. The pattern that applies here is straightforward: since linked lists are linear data structures, we can traverse ...
Approach
- Initialize an empty list to hold the values we encounter during our DFS traversal.
- Define a recursive function that takes a node as input:
- If the node is
None, return (base case)....
- If the node is
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