[BFS] BOJ 7576 토마토

import sys
from collections import deque
input = sys.stdin.readline
 
M, N = map(int, input().split())
box = [list(map(int, input().split())) for _ in range(N)]
DELTAS = ((1, 0), (0, 1), (-1, 0), (0, -1))
visited = [[-1] * M for _ in range(N)]
def bfs(arr, visited):
    queue = deque()
 
    # queue 초기화
    for i in range(N):
        for j in range(M):
            if arr[i][j] == 1:
                queue.append((i, j))
                visited[i][j] = 0
            elif arr[i][j] == -1:
                visited[i][j] = 0
 
    # bfs
    while queue:
        y, x = queue.popleft()
        for dy, dx in DELTAS:
            ny = y + dy 
            nx = x + dx 
            if ny < 0 or ny >= N or nx < 0 or nx >= M: continue
            if visited[ny][nx] == -1 and arr[ny][nx] == 0:
                queue.append((ny, nx))
                visited[ny][nx] = visited[y][x] + 1 # 익은 날짜 추가 
 
 
def print_answer(visited):
    answer = 0
    for row in visited:
        answer = max(max(row), answer)
        for ele in row:
            if ele == -1:
                return -1 
    return answer
 
bfs(box, visited)
print(print_answer(visited))