BFS on linked list
Last updated: July 20, 2025
Quick Overview
Implement a breadth-first search (BFS) algorithm to traverse a linked list. Given the head of a singly linked list, return the values of the nodes in the order they are visited using BFS. The output should be a list of values collected during the traversal.
Slack
July 20, 202540
14
2,928 solved
Implement a breadth-first search (BFS) algorithm to traverse a linked list. Given the head of a singly linked list, return the values of the nodes in the order they are visited using BFS. The output should be a list of values collected during the traversal.
Slack uses this problem in the Onsite 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
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
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)?
- What is the worst-case input for your solution?
- What happens if the input contains duplicates?
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Practice DSA ProblemsSample Answer
Problem Analysis
In this problem, we are required to implement a breadth-first search (BFS) on a singly linked list. The BFS algorithm is typically used for traversing tree or graph-like structures, but in this case, ...
Approach
- Initialize an empty list
resultto store the values of the nodes we visit. - Start with the head of the linked list and enqueue it to a queue (we can use a simple list to mimic a queue).
- Wh...
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