Rotting Oranges

You have a grid with:

• 0: Empty cell
• 1: Fresh orange
• 2: Rotten orange

Every minute, a rotten orange infects its 4-directionally adjacent fresh neighbors. Return minimum minutes until no fresh orange remains. If impossible, return -1.

This simulates a process expanding over time, which is classic BFS.

1. Multi-source: Start with ALL initially rotten oranges in the Queue.
2. Count Fresh: Count total fresh oranges initially. If 0, return 0.
3. Level-by-Level: Process the queue layer by layer (minutes). Each layer spreads rot to neighbors.
   • Decrement fresh_count whenever a fresh orange rots.
4. Completion: If queue empty and fresh_count == 0, return time. Else return -1.

Watch how the infection spreads from multiple sources simultaneously.