在python中使用BFS算法解决UVA问题

如何解决在python中使用BFS算法解决UVA问题

我在 Python 中遇到以下问题：https://onlinejudge.org/index.php?option=onlinejudge&page=show_problem&problem=1594

这是我的代码：

from queue import Queue

MAX = 1001
table = [[0] * MAX for i in range(MAX)]
dist = [[0] * MAX for i in range(MAX)]

dr = [0,-1,1]
dc = [-1,1,0]

def BFS(sr,sc,fr,fc):
    q = Queue()
    q.put((sr,sc))

    while not q.empty():
        ur,uc = q.get()

        for i in range(4):
            rr = ur + dr[i]
            cc = uc + dc[i]

            if rr == fr and cc == fc:
                dist[rr][cc] = dist[ur][uc] + 1
                return

            if rr in range(r) and cc in range(c) and table[rr][cc] != 1:
                q.put((rr,cc))
                dist[rr][cc] = dist[ur][uc] + 1

while True:
    r,c = map(int,input().split())
    if r == 0 and c == 0:
      exit()

    # Reset variable
    for i in range(r):
        for j in range(c):
            table[i][j] = 0
            dist[i][j] = 0

    row = int(input())
    for i in range(row):
      b = list(map(int,input().split()))
      for j in range(2,len(b)):
          table[i][b[j]] = 1

    sr,sc = map(int,input().split())
    fr,fc = map(int,input().split())
    BFS(sr,fc)

    print(dist[fr][fc])

谁能帮我指出代码中的错误？它不返回任何东西。非常感谢。