Question
A grid models a warehouse where each cell is 0 (empty), 1 (a healthy unit), or 2 (a contaminated unit). Every minute, each contaminated unit spreads to its orthogonally adjacent healthy units, contaminating them. Return the minimum number of minutes until no healthy unit remains, or -1 if some healthy unit can never be reached. If there are no healthy units 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.