質問する

コード#コード#

import sys
input = sys.stdin.readline
from collections import deque #BFS

m,n = map(int,input().split())

dx = [1,-1,0,0]
dy = [0,0,-1,1]

queue = deque()
graph=[]

for i in range(n):
    graph.append(list(map(int, input().rstrip().split())))

#붙이기 

#익은토마토 조사 
for i in range(n):
    for j in range(m):
        if graph[i][j]==1:
            queue.append([i,j])

def bfs():
  while queue:
      a,b = queue.popleft() #i.j삽입 
      for i in range(4):
          cx = a+dx[i]
          cy = b+dy[i]
          if 0<=cx<n  and 0<=cy<m and graph[cx][cy]==0: 
              graph[cx][cy] = graph[a][b] + 1 #시간 더해나감 
              queue.append([cx,cy])
# print(graph)
bfs()
flag = 1 # 1 익음 0 안익음  
time = -2 
# print(graph)
for j in graph:
    for k in j:
        if k==0: #익지 않은것이 존재 
            flag =0 #안익음... 
        time =max(time,k)

if time == 1 : #최댓값이 1 #다익음   
    print(0)
elif flag ==0: #안익은게 있음/// 
    print(-1)
else :
    print(time - 1) #1초부터 시작하니 1빼줌 

解説

BFS