BFS on array
Last updated: April 7, 2026
Quick Overview
Implement a Breadth-First Search (BFS) algorithm to traverse a given array, treating it as a level-order representation of a binary tree. Your function should return the elements in the order they are visited during the BFS traversal. The input will be a non-empty array of integers, and the output should be an array of integers representing the traversal order.
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Implement a Breadth-First Search (BFS) algorithm to traverse a given array, treating it as a level-order representation of a binary tree. Your function should return the elements in the order they are visited during the BFS traversal. The input will be a non-empty array of integers, and the output should be an array of integers representing the traversal order.
This coding problem is frequently asked during Take-home Project at LinkedIn. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. LinkedIn 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
- How would your solution change if the input was sorted?
- What happens if the input contains duplicates?
- What is the worst-case input for your solution?
- How would you parallelize this solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires implementing a Breadth-First Search (BFS) algorithm on an array representing a level-order traversal of a binary tree. The BFS pattern is appropriate here because it systematicall...
Approach
- Initialize a queue to facilitate the BFS. Start by enqueuing the index of the root node, which is 0.
- Create a result list to store the traversal order of the nodes.
- **While the qu...
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