Your free access ends in 7 days — and you haven’t tried it yet. Watch one algorithm run, start to finish. It takes about two minutes.
Try one problemGiven a grid whose cells are empty, hold a fresh orange, or hold a rotten orange, each minute every fresh orange adjacent to a rotten one becomes rotten; return the minimum number of minutes until no fresh orange remains, or -1 if some fresh orange can never rot.
▸1queue = all rotten cells // multi-source seed2fresh = count of 1s3minute = 04while queue not empty and fresh > 0:5 minute++6 for each cell in this minute’s batch:7 for each fresh neighbour:8 rot it, fresh--, enqueue it9 queue = newly rotted10return fresh == 0 ? minute : -1
line 1Rotting Oranges: every minute, each rotten orange (2) rots its four fresh neighbours (1). We want the minute when the LAST fresh orange rots. The rot spreads outward in rings — exactly one cell-step per minute — which is precisely what BFS levels measure. So this is a shortest-time-to-infect problem.