BFS on matrix
Last updated: January 19, 2026
Quick Overview
Implement a Breadth-First Search (BFS) algorithm to traverse a given 2D matrix, where each cell can either be a passable space (0) or an obstacle (1). Your task is to find the shortest path from a starting cell to a target cell, returning the length of the path if it exists, or -1 if there is no valid path. The matrix will be provided as input, along with the coordinates of the starting and target cells.
Adobe
January 19, 20262
9
3,702 solved
Implement a Breadth-First Search (BFS) algorithm to traverse a given 2D matrix, where each cell can either be a passable space (0) or an obstacle (1). Your task is to find the shortest path from a starting cell to a target cell, returning the length of the path if it exists, or -1 if there is no valid path. The matrix will be provided as input, along with the coordinates of the starting and target cells.
Coding interviews at Adobe focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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 you modify your solution to handle streaming input?
- How would you parallelize this solution?
- How would your solution change if the input was sorted?
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Problem Analysis
In this problem, we need to find the shortest path in a 2D matrix where each cell is either passable (0) or an obstacle (1). This scenario is well-suited for a Breadth-First Search (BFS) algorithm bec...
Approach
- Initialize a queue and add the starting position to it, along with a step count of 0. Keep track of visited cells using a set to avoid processing the same cell multiple times.
- **Define possi...
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