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It's LeetCode 994 with a coat of paint, which I actually recognized pretty quickly.
Model the grid as a graph and use multi-source BFS to simulate the popping process, where each minute represents a BFS layer. Track the maximum distance from any initially popped balloon to determine the total minutes, and check if all balloons are popped; if not, return -1.
Pro tip: Clarify the neighbor definition (4-directional vs 8-directional) and whether diagonal adjacency counts, as this significantly affects the solution. Also, discuss edge cases like empty grids or grids with no initially popped balloons.
Ask about neighbor definition (4 or 8 directions), grid dimensions, and whether the grid can contain obstacles or only balloons. Confirm that popping propagates simultaneously each minute.
Treat each balloon as a node and edges between adjacent balloons. Initially popped balloons are sources for BFS.
Initialize a queue with all initially popped balloons and set their distance to 0. Perform BFS, updating distances for unvisited neighbors and enqueueing them. Track the maximum distance encountered.
After BFS, verify if all balloons have been visited. If yes, return the maximum distance; otherwise, return -1.
State time and space complexity: O(R*C) for BFS, where R and C are grid dimensions, as each cell is processed once.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.