leetcode 200 python

題目要求：
https://leetcode-cn.com/problems/number-of-islands/

class Solution:
    def numIslands(self, grid: List[List[str]]) -> int:
        if not grid: return 0
        row = len(grid)
        col = len(grid[0])
        cnt = 0

        def dfs(i, j):
            grid[i][j] = "0"
            for x, y in [[-1, 0], [1, 0], [0, -1], [0, 1]]:
                tmp_i = i + x
                tmp_j = j + y
                if 0 <= tmp_i < row and 0 <= tmp_j < col and grid[tmp_i][tmp_j] == "1":
                    dfs(tmp_i, tmp_j)

        for i in range(row):
            for j in range(col):
                if grid[i][j] == "1":
                    dfs(i, j)
                    cnt += 1
        return cnt