Counting Rooms

#include <bits/stdc++.h>

using namespace std;

int n, m;
char grid[1001][1001];
bool visited[1001][1001];
int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, 1, -1};
int ans;

void dfs(int x, int y){
    if(visited[x][y] || x<0 || x>n-1 || y<0 || y>m-1){
        return;
    }
    //cout << "x: " << x << ", y: " << y << '\n';
    visited[x][y] = true;
    for(int i=0; i<4; i++){
        int nx = x+dx[i];
        int ny = y+dy[i];
        //cout << "nx: " << nx << ", ny: " << ny << '\n';
        if(!visited[nx][ny] && nx>=0 && nx<=n-1 && ny>=0 && ny<=m-1 && grid[nx][ny] == '.'){
            dfs(nx, ny);
        }
    }
}

int main(){
    //freopen("rooms.in", "r", stdin);

    cin >> n >> m;
    string s;
    for(int i=0; i<n; i++){
        cin >> s;
        for(int j=0; j<m; j++){
            grid[i][j] = s[j];
            //if(grid[i][j] == '.') cout << " ";
            //cout << grid[i][j];
        }
        //cout << '\n';
    }
    for(int i=0; i<n; i++){
        for(int j=0; j<m; j++){
            if(!visited[i][j] && grid[i][j] == '.'){
                //cout << "i: " << i << ", j: " << j << ", grid[i][j]: " << grid[i][j] << '\n';
                ans++;
                dfs(i, j);
            }
        }
    }
    cout << ans << '\n';

    return 0;
}