RottingOranges.py

//Python 3 Solution

import numpy as np

class Solution:
    def orangesRotting(self, grid: List[List[int]]) -> int:
        rotten = []
        r, c, fresh, t = len(grid), len(grid[0]), 0, 0
        for i in range(r):
            for j in range(c):
                if grid[i][j] == 2: rotten.append([i, j])
                elif grid[i][j] == 1: fresh += 1
        
        while len(rotten) > 0:
            num = len(rotten)
            for i in range(num):
                x, y = rotten[0]
                rotten.pop(0);
                if x > 0 and grid[x-1][y] == 1: grid[x-1][y] = 2; fresh -= 1; rotten.append([x-1, y])
                if y > 0 and grid[x][y-1] == 1: grid[x][y-1] = 2; fresh -= 1; rotten.append([x, y-1])
                if x < r-1 and grid[x+1][y] == 1: grid[x+1][y] = 2; fresh -= 1; rotten.append([x+1, y])
                if y < c-1 and grid[x][y+1] == 1: grid[x][y+1] = 2; fresh -= 1; rotten.append([x, y+1])
            if len(rotten) > 0: t += 1
        
        return t if (fresh == 0) else -1