994. Rotting Oranges

Practice Rotting Oranges for free on NudgeCode: Medium, Graph pattern. Write it in Python or JavaScript, run the tests in your browser, and ask for a hint when you are stuck.

Each cell of grid is 0 (empty), 1 (fresh orange) or 2 (rotten orange). Every minute, each fresh orange that is directly up, down, left or right of a rotten orange becomes rotten. Return the number of minutes until no fresh orange is left, or -1 if some fresh orange can never rot.

Example

grid = [[2,1,1],
        [1,1,0],
        [0,1,1]]  ->  4

Constraints

• 1 <= m, n <= 20 (m rows, n columns)
• grid[i][j] is 0, 1 or 2