Python

import sys
sys.setrecursionlimit(10**7)

n, m = map(int, input().split())
gridIsFloor = []
visitedRoom = [[False] * m for _ in range(n)]

for i in range(n):
    row = input()
    gridIsFloor.append([c == '.' for c in row])
    for j in range(m):
        if not gridIsFloor[i][j]:
            visitedRoom[i][j] = True

def traverse(x, y):
    if x < 0 or x >= n or y < 0 or y >= m:
        return
    if visitedRoom[x][y]:
        return
    if not gridIsFloor[x][y]:
        return
    visitedRoom[x][y] = True
    traverse(x + 1, y)
    traverse(x - 1, y)
    traverse(x, y + 1)
    traverse(x, y - 1)

numberOfRooms = 0
for i in range(n):
    for j in range(m):
        if visitedRoom[i][j]:
            continue
        numberOfRooms += 1
        traverse(i, j)

print(numberOfRooms)

Java

import java.util.Scanner;

public class Main {
    static int n, m;
    static boolean[][] gridIsFloor;
    static boolean[][] visitedRoom;

    static void traverse(int x, int y) {
        if (x < 0 || x >= n || y < 0 || y >= m) return;
        if (visitedRoom[x][y]) return;
        if (!gridIsFloor[x][y]) return;
        visitedRoom[x][y] = true;
        traverse(x + 1, y);
        traverse(x - 1, y);
        traverse(x, y + 1);
        traverse(x, y - 1);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();
        sc.nextLine();

        gridIsFloor = new boolean[n][m];
        visitedRoom = new boolean[n][m];

        for (int i = 0; i < n; i++) {
            String line = sc.nextLine();
            for (int j = 0; j < m; j++) {
                char c = line.charAt(j);
                if (c == '.') {
                    gridIsFloor[i][j] = true;
                } else {
                    visitedRoom[i][j] = true;
                }
            }
        }

        int numberOfRooms = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (visitedRoom[i][j]) continue;
                numberOfRooms++;
                traverse(i, j);
            }
        }
        System.out.println(numberOfRooms);
        sc.close();
    }
}

C++

#include <bits/stdc++.h>
using namespace std;
int n, m;
bool gridIsFloor[1005][1005];
bool visitedRoom[1005][1005];

void traverse(int x, int y) {
    if (x < 0 || x >= n || y < 0 || y >= m) return;
    if (visitedRoom[x][y]) return;
    if (!gridIsFloor[x][y]) return;
    visitedRoom[x][y] = true;
    traverse(x + 1, y);
    traverse(x - 1, y);
    traverse(x, y + 1);
    traverse(x, y - 1);
}

signed main() {
    cin.sync_with_stdio(0);
    cin.tie(0);
    cin >> n >> m;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            char c;
            cin >> c;
            if (c == '.') {
                gridIsFloor[i][j] = true;
            } else visitedRoom[i][j] = true;
        }
    }
    int numberOfRooms = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            if (visitedRoom[i][j]) continue;
            numberOfRooms++;
            traverse(i, j);
        }
    }
    cout << numberOfRooms << endl;
}