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Java-based LeetCode algorithm problem solutions, regularly updated
994\. Rotting Oranges
Medium
You are given an `m x n` `grid` where each cell can have one of three values:
* `0` representing an empty cell,
* `1` representing a fresh orange, or
* `2` representing a rotten orange.
Every minute, any fresh orange that is **4-directionally adjacent** to a rotten orange becomes rotten.
Return _the minimum number of minutes that must elapse until no cell has a fresh orange_. If _this is impossible, return_ `-1`.
**Example 1:**
![](https://assets.leetcode.com/uploads/2019/02/16/oranges.png)
**Input:** grid = [[2,1,1],[1,1,0],[0,1,1]]
**Output:** 4
**Example 2:**
**Input:** grid = [[2,1,1],[0,1,1],[1,0,1]]
**Output:** -1
**Explanation:** The orange in the bottom left corner (row 2, column 0) is never rotten, because rotting only happens 4-directionally.
**Example 3:**
**Input:** grid = [[0,2]]
**Output:** 0
**Explanation:** Since there are already no fresh oranges at minute 0, the answer is just 0.
**Constraints:**
* `m == grid.length`
* `n == grid[i].length`
* `1 <= m, n <= 10`
* `grid[i][j]` is `0`, `1`, or `2`.