BFS is the obvious move here and I got there pretty fast.
Use BFS to find the shortest path in an unweighted grid, tracking parent pointers to reconstruct the path. Start by clarifying the problem constraints, then explain the BFS algorithm, and finally discuss path reconstruction and complexity.
Pro tip: Mention that BFS is optimal for unweighted grids and that using a queue ensures the first time you reach the end is the shortest path. Also, discuss how to handle edge cases like no path or start equals end.
Ask about grid dimensions, movement rules, and whether diagonal moves are allowed. Confirm that the grid is unweighted and that you need the shortest path length and the actual path.
Explain that BFS is ideal for finding the shortest path in an unweighted graph. Mention that each cell is a node, and edges connect adjacent open cells.
Use a queue to explore level by level, marking visited cells. Store the parent of each visited cell to reconstruct the path later.
Once the end is reached, backtrack from the end to the start using the parent pointers to build the path. If the queue empties without reaching the end, return no path.
State that time complexity is O(R*C) where R and C are grid dimensions, and space complexity is O(R*C) for the queue and visited set.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.