Leetcode 200. Number of Islands

class Solution:
    def numIslands(self, grid: List[List[str]]) -> int:    
        count = 0
        
        for i in range(len(grid)):
            for j in range(len(grid[0])):
                if grid[i][j] == '1':
                    self.dfs(grid, i, j)
                    count += 1
        
        return count
    
    def dfs(self, grid, i, j):
        print(i, j)
        if i < 0 or j < 0 or i >= len(grid) or j >= len(grid[0]) or grid[i][j] != '1' or grid[i][j] == '#':
            return
        
        grid[i][j] = '#'
        
        self.dfs(grid, i-1, j)
        self.dfs(grid, i+1, j)
        self.dfs(grid, i, j-1)
        self.dfs(grid, i, j+1)

https://leetcode.com/problems/number-of-islands/