python 代码

from collections import deque
import sys
mp = []
for line in sys.stdin:
    line = line.strip()
    if not line:
        break
    row = list(map(int, line.split()))
    mp.append(row)
dx = [1,-1,0,0]
dy = [0,0,1,-1]
n = len(mp)
m = len(mp[0])
time = [[float('inf') for i in range(m)] for j in range(n)]
def bfs():
    q = deque()
    for i in range(n):
        for j in range(m):
            if mp[i][j] == 2:
                time[i][j] = 0
                q.append((i,j))
    while q:
        t = q.popleft()
        for i in range(4):
            x = t[0] + dx[i]
            y = t[1] + dy[i]
            if x < 0 or x >= n or y < 0 or y >= m:
                continue
            if mp[x][y] == 0:
                continue
            if mp[x][y] == 2:
                if time[x][y] > time[t[0]][t[1]] + 1:
                    time[x][y] = time[t[0]][t[1]] + 1
                    q.append((x,y))
                continue
            mp[x][y] = 2
            time[x][y] = time[t[0]][t[1]] + 1
            q.append((x,y))
bfs()
res = 0
for i in range(n):
    for j in range(m):
        if mp[i][j] == 1:
            print(-1)
            exit()
        if mp[i][j] == 0:
            continue
        res = max(res,time[i][j])
print(res)