[Leetcode depth-first search C++] 200. Number of Islands

200. Number of Islands

class Solution {
    
    
public:
    int H, W;
    int cnt = 0;
    void dfs(int y, int x, vector<vector<char> >& grid, vector<vector<bool> >& visited) {
    
    
        if(y < 0 || y >= H || x < 0 || x >= W || visited[y][x] || grid[y][x] == '0') return ;
        visited[y][x] = true;
        dfs(y-1, x, grid, visited);
        dfs(y+1, x, grid, visited);
        dfs(y, x-1, grid, visited);
        dfs(y, x+1, grid, visited);
    }
    int numIslands(vector<vector<char>>& grid) {
    
    
        H = grid.size();
        W = grid[0].size();
        vector<vector<bool> > visited(H, vector<bool>(W, false));
        for(int ii = 0; ii < H; ii++) {
    
    
            for(int jj = 0; jj < W; jj++) {
    
    
                if(!visited[ii][jj] && grid[ii][jj] == '1') {
    
    
                    dfs(ii, jj, grid, visited);
                    cnt++;
                }
            }
        }
        return cnt;
    }
};