题解 | 岛屿数量

#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 判断岛屿数量
# @param grid char字符型二维数组 
# @return int整型
#
class Solution:
    def solve(self , grid: List[List[str]]) -> int:
        # write code here
        if not grid:
            return 0
        n, m = len(grid), len(grid[0])
        def dfs(i,j):
            if 0<=i<n and 0<=j<m and grid[i][j]=='1':
                grid[i][j] = '0'
            else:
                return 
            dfs(i+1,j)
            dfs(i-1,j)
            dfs(i,j+1)
            dfs(i,j-1)
        ans = 0
        for i in range(n):
            for j in range(m):
                if grid[i][j]=='1':
                    ans += 1
                    dfs(i,j)
        return ans