BFS on graph
Last updated: November 2, 2025
Quick Overview
Implement the Breadth-First Search (BFS) algorithm to traverse a given undirected graph represented as an adjacency list. Your function should take the starting node as input and return a list of nodes in the order they are visited. Ensure that your solution handles graphs with cycles and disconnected components appropriately.
Anduril
November 2, 202569
6
4,804 solved
Implement the Breadth-First Search (BFS) algorithm to traverse a given undirected graph represented as an adjacency list. Your function should take the starting node as input and return a list of nodes in the order they are visited. Ensure that your solution handles graphs with cycles and disconnected components appropriately.
This coding problem is frequently asked during Technical Screen at Anduril. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Anduril expects candidates to write production-quality code, not just solve the puzzle.
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
- What if the input doesn't fit in memory?
- Can you solve this iteratively instead of recursively (or vice versa)?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To effectively traverse an undirected graph, we will utilize the Breadth-First Search (BFS) algorithm. BFS is well-suited for this problem due to its level-order traversal nature, which explores all n...
Approach
The BFS algorithm will be implemented as follows:
- Initialization: Create a queue to hold nodes to be explored, and a set to keep track of visited nodes. Start by enqueueing the given starting n...
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