BFS on grid
Last updated: October 4, 2025
Quick Overview
Implement the Breadth-First Search (BFS) algorithm to traverse a 2D grid represented as a matrix, where each cell can either be passable (0) or blocked (1). Your task is to find the shortest path from the top-left corner of the grid to the bottom-right corner, returning the length of the path, or -1 if no path exists. The grid will be provided as input, and the output should be an integer representing the path length.
Uber
October 4, 202550
7
1,602 solved
Implement the Breadth-First Search (BFS) algorithm to traverse a 2D grid represented as a matrix, where each cell can either be passable (0) or blocked (1). Your task is to find the shortest path from the top-left corner of the grid to the bottom-right corner, returning the length of the path, or -1 if no path exists. The grid will be provided as input, and the output should be an integer representing the path length.
Coding interviews at Uber 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
- 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 optimize the space complexity of your solution?
- How would your solution change if the input was sorted?
- What happens if the input contains duplicates?
Sharpen Your Skills on Codemia
Practice similar problems with our interactive workspace, get AI feedback, and track your progress.
Practice DSA ProblemsSample Answer
Problem Analysis
This problem can be effectively solved using the Breadth-First Search (BFS) algorithm due to its nature of exploring all possible paths layer by layer, making it ideal for finding the shortest path in...
Approach
- Initialize the BFS Queue: Start by adding the starting cell (0, 0) to the queue and marking it as visited.
- Define Directions: Create a list of possible moves (up, down, left, right) to ...
Submit Your Answer
