Rotting Oranges

Rotting Oranges

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.

Examples

Example 1:

Input: grid = [[2,1,1],[1,1,0],[0,1,1]]
Output: 4
Explanation: The rotten orange at (0,0) spreads to adjacent
fresh oranges each minute. After 4 minutes, all oranges are rotten.

Example 2:

Input: grid = [[2,1,1],[0,1,1],[1,0,1]]
Output: -1
Explanation: The orange at (2,2) can never be reached because
it is isolated from the rotten orange.

Example 3:

Input: grid = [[0,2]]
Output: 0
Explanation: There are no fresh oranges, so 0 minutes are needed.

Constraints

• m == grid.length
• n == grid[i].length
• 1 <= m, n <= 10
• grid[i][j] is 0, 1, or 2

Expected Complexity

• Time: O(m * n)
• Space: O(m * n)