蔚来 面试

1 求图中的水域个数：岛屿数量

输入： grid = [  ["1","1","1","1","0"],
  ["1","1","0","1","0"],
  ["1","1","0","0","0"],
  ["0","0","0","0","0"]
]
输出： 1

2 有向图判断环