https://leetcode.com/problems/rotting-oranges/submissions/

rottingOranges.py

from collections import deque

class Solution:
    def orangesRotting(self, grid: List[List[int]]) -> int:
        
        q = deque()
        seen = set()
        maxDay = 0
        
        for row in range(len(grid)):
            for col in range(len(grid[row])):
                if grid[row][col] == 2:
                    q.append((row, col, 0))
                    
        while(len(q)):
            i, j, day = q.popleft()
            
            if (i, j) in seen:
                continue
            
            seen.add((i, j))
            maxDay = max(maxDay, day)
            grid[i][j] = 2
            
            adjacent = [(i+1, j),(i-1, j),(i, j+1),(i, j-1)]
            
            for y, x in adjacent: # for all neighboring fresh oranges
                if y>-1 and y<len(grid) and\
                x>-1 and x<len(grid[0]) and\
                (y, x) not in seen and\
                grid[y][x] == 1:
                    q.append((y, x, day+1)) # add to queue
                    
        
        # check no fresh oranges still exit
        for row in range(len(grid)):
            for col in range(len(grid[row])):
                if grid[row][col] == 1:
                    return -1

        return maxDay