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Posted 2021-02-15 astonc

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
const int MAX = 100;
int N, M, cnt;
char maze[MAX][MAX];
bool vis[MAX][MAX];
int sx, sy;
int dir[4][2] = {1, 0, -1, 0, 0, 1, 0, -1};
int bfs () {
    //cout<<"1"<<endl;
    queue<pair<int, int> > q;
    int cnt = 0;
    q.push(make_pair(sx, sy));
    vis[sx][sy] = true;
    while (!q.empty()) {
        int x = q.front().first;
        int y = q.front().second;
        q.pop() ;
        for (int i = 0; i < 4; i++) {
            int nx = x + dir[i][0];
            int ny = y + dir[i][1];
            if(nx >= 0 && nx < N && ny >= 0 && ny < M && maze[nx][ny] == ‘.‘ && vis[nx][ny] == false) {
                vis[nx][ny] = true;
                q.push(make_pair(nx, ny)); 
            }
        }
        cnt++;
    }
    return cnt;
}

int main () {
    while (cin >> N >> M && N != 0) {
    //while (~scanf("%d%d", &N, &M) && N != 0) {
        //getchar();
        swap(N,M);
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < M; j++) {
                //scanf("%c", &maze[i][j]);
                cin >> maze[i][j];
                if (maze[i][j] == ‘@‘) {
                    sx = i;
                    sy = j;
                }
            }
            //getchar();
        }
        memset (vis, false, sizeof(vis));
        int ans = bfs();
        printf("%d
", ans);
    }
    
    
}