Rotting Oranges (Multi-source BFS) in Java: Explanation & Practice

Problem summary

In a grid, 0=empty, 1=fresh orange, 2=rotten. Every minute, fresh oranges adjacent to rotten ones become rotten. Return minimum minutes until no fresh orange remains.

Starter code

public class Main {
    public static void main(String[] args) {
        int[][] grid = {
            {2,1,1},
            {1,1,0},
            {0,1,1}
        };
        
        // Multi-source BFS: start from ALL rotten oranges
        // Each BFS level = 1 minute
        // Print: Minutes: 4
    }
}

Expected output and test cases

• 4 minutes to rot all

  Minutes: 4

• Isolated fresh orange

  Minutes: -1

• No fresh oranges

  Minutes: 0

Hints

1. Add ALL initial rotten oranges to queue
2. BFS level by level, each level = 1 minute
3. Count fresh oranges initially
4. Decrement count as oranges rot; if count > 0 at end, return -1

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