Question
Given an R x C grid where each cell is 0 (empty), 1 (susceptible), or 2 (already activated), each minute every activated cell activates its 4-directionally adjacent susceptible cells simultaneously. Return the minimum number of minutes until no susceptible cell remains, or -1 if some susceptible cell can never be reached. If there are no susceptible cells initially, return 0.
spread_time(grid: list[list[int]]) → int[[[2,1,1],[1,1,0],[0,1,1]]]out4State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.