Counting Rooms.cpp

#include <bits/stdc++.h>

using namespace std;

char c;
int N, M, cnt;
int h[] = {1, -1, 0, 0}, v[] = {0, 0, 1, -1};
bool vis[1000][1000];

void dfs(int x, int y){
    vis[x][y] = true;
    for(int i = 0; i < 4; i++){
        int dx = x+h[i], dy = y+v[i];
        if(0 <= dx && dx < N && 0 <= dy && dy < M && !vis[dx][dy])
            dfs(dx, dy);
    }
}

int main(){
    scanf("%d %d", &N, &M);
    for(int i = 0; i < N; i++){
        for(int j = 0; j < M; j++){
            scanf(" %c", &c);
            vis[i][j] = (c == '#');
        }
    }
    for(int i = 0; i < N; i++){
        for(int j = 0; j < M; j++){
            if(!vis[i][j]){
                dfs(i, j);
                cnt++;
            }
        }
    }
    printf("%d\n", cnt);
}