Classic BFS and I knew it immediately, which almost made it worse because I started overthinking edge cases instead of just writing the code.
Recognize this as a shortest path problem on an unweighted grid and apply BFS from the start position, exploring all four directions while avoiding walls and visited cells. Return the distance when the cheese is reached, or -1 if the queue is exhausted without finding it.
Pro tip: Mention that BFS is optimal for unweighted grids because it explores level by level, guaranteeing the first time you reach the cheese is the shortest path. Also, discuss edge cases like start equals cheese, no path, and large grids to show thoroughness.
Confirm grid dimensions, movement rules (4-directional), and what constitutes a wall or open cell. Ask about edge cases like start equals cheese or no path.
Explain that BFS is ideal for finding the shortest path in an unweighted graph, as it explores nodes in increasing order of distance from the start.
Describe using a queue to store cells and their distances, a visited set to avoid revisiting, and iterating through the four directions for each cell.
Return the distance when the cheese is dequeued or reached; if the queue empties, return -1. Also handle start equals cheese by returning 0 immediately.
State that time and space complexity are O(rows * cols) in the worst case. Mention possible optimizations like bidirectional BFS if needed.
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