Baekjoon-17086-아기 상어 2

import sys
input = sys.stdin.readline
sys.setrecursionlimit(10000)

N,M = map(int, input().split())
maps = [[0 for _ in range(M)] for _ in range(N)]

queue = []
visited = [[-1 for _ in range(M)] for _ in range(N)]
# build map
for n in range(N):
    row = list(map(int, input().split()))
    for m in range(M):
        maps[n][m] = row[m]
        if row[m] == 1:
            queue.append((n,m)) # put shark

max_dist = 0
while queue:
    i,j = queue.pop(0)
    if maps[i][j] == 1:
        visited[i][j] = 0
    
    for u,v in [(i+1,j+1), (i+1,j), (i+1,j-1), (i,j+1), (i,j-1), (i-1,j+1), (i-1,j), (i-1,j-1)]:
        if (0 <= u < N) and (0 <= v < M):
            if visited[u][v] == -1:
                visited[u][v] = visited[i][j] + 1
                max_dist = max(max_dist, visited[u][v])
                queue.append((u,v))

print(max_dist)