CSES – Counting Rooms

#include<bits/stdc++.h>
#define int long long
#define double long double
#define f first
#define s second
#define fastio ios_base::sync_with_stdio(false);cin.tie(0)
using namespace std;
int n,m;
char maze[1005][1005];
int dir[4][2] = {{0,1},{0,-1},{1,0},{-1,0}};
void dfs(int x,int y,int lastx,int lasty){
    maze[x][y] = '#';
    for(int i=0;i<4;i++){
        int nx = x+dir[i][0], ny = y+dir[i][1];
        if(lastx == nx && lasty == ny) continue;
        if(maze[nx][ny] == '#') continue;
        dfs(nx,ny,x,y);
    }
}
signed main(){
    fastio;
    cin>>n>>m;
    memset(maze,'#',sizeof(maze));
    for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) cin>>maze[i][j];
    int cnt=0;
    for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) if(maze[i][j] == '.') dfs(i,j,-1,-1), cnt++;
    cout<<cnt<<"\n";
    return 0;
}