200

class Solution {
int row, col;
public:
    int numIslands(vector<vector<char>>& grid) {
        row = grid.size();
        col = grid[0].size();
        int components = 0;
        for(int i=0; i<row; i++)
            for(int j=0; j<col; j++)
                if(grid[i][j] == '1')
                    components++, dfs(i, j, grid);
        return components;
    }

    void dfs(int r, int c, vector<vector<char>> &grid){
        if(r<0 || r >= row || c<0 || c>=col || grid[r][c] == '0') return;
        grid[r][c] = '0';
        dfs(r+1, c, grid);
        dfs(r-1, c, grid);
        dfs(r, c+1, grid);
        dfs(r, c-1, grid);
    }
};