289. Rotting Oranges
Medium•
You are given an m x n grid where each cell can be 0 (empty), 1 (fresh orange), or 2 (rotten orange).
Every minute, fresh oranges adjacent up, down, left, or right to a rotten orange become rotten. Return the minimum minutes needed to rot all oranges, or -1 if some fresh orange is unreachable.
Example 1:
Input: orangesRotting([[2,1,1],[1,1,0],[0,1,1]])
Output: 4
Explanation: After minute 1, the rot reaches the adjacent oranges. After minute 2, it spreads one step farther, and after minute 4, every fresh orange has become rotten.
Example 2:
Input: orangesRotting([[2,1,1],[0,1,1],[1,0,1]])
Output: -1
Explanation: Some fresh oranges are unreachable from any rotten source.
Constraints
- 1 <= m, n <= 100
- Grid values are 0,1,2
- Use multi-source BFS
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