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# Rotting Oranges

In a given grid, each cell can have one of three values:

* the value `0` representing an empty cell;
* the value `1` representing a fresh orange;
* the value `2` representing a rotten orange.

Every minute, any fresh orange that is adjacent (4-directionally) 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` instead.

**Example 1:**

![](https://assets.leetcode.com/uploads/2019/02/16/oranges.png)

```
Input: [[2,1,1],[1,1,0],[0,1,1]]
Output: 4
```

**Example 2:**

```
Input: [[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: [[0,2]]
Output: 0
Explanation:  Since there are already no fresh oranges at minute 0, the answer is just 0.
```

**Note:**

1. `1 <= grid.length <= 10`
2. `1 <= grid[0].length <= 10`
3. `grid[i][j]` is only `0`, `1`, or `2`.

```java
class Solution {
    public int orangesRotting(int[][] grid) {
        int totalOranges = 0;
        Queue<int[]> q = new LinkedList<>();
        for (int i = 0; i < grid.length; i++)
            for (int j = 0; j < grid[i].length; j++) {
                if (grid[i][j] == 2)
                    q.add(new int[] { i, j });
                if (grid[i][j] == 1 || grid[i][j] == 2)
                    totalOranges++;
            }
        int[][] dir = { { 1, 0 }, { 0, 1 }, { -1, 0 }, { 0, -1 } };
        int minutes = 0, rottenOranges = 0;
        while (q.size() != 0) {
            int size = q.size();
            while (size-- > 0) {
                int[] pos = q.poll();
                for (int i = 0; i < 4; i++) {
                    int x = pos[0] + dir[i][0];
                    int y = pos[1] + dir[i][1];
                    if (x >= 0 && x < grid.length && y >= 0 && y < grid[x].length && grid[x][y] == 1) {
                        grid[x][y] = 2;
                        q.add(new int[] { x, y });
                    }
                }
                rottenOranges++;
            }
            if (q.size() != 0)
                minutes++;
        }
        return rottenOranges == totalOranges ? minutes : -1;
    }
}
```