C++ 代码

#include<bits/stdc++.h>
using namespace std;

#define x first
#define y second
typedef pair<int, int> PII;

const int N = 25;
char g[N][N];
int n, m;
int cnt;
int dir[4][2] = { 1,0,-1,0,0,-1,0,1 };
int vis[N][N];

bool check(int x, int y)
{
    if (x >= 0 && x < n && y >= 0 && y < m && g[x][y] == '.')return true;
    else return false;
}

void bfs(PII s)
{
    queue<PII> q;
    q.push(s); cnt = 1;

    while (q.size())
    {
        auto t = q.front(); q.pop();
        for (int i = 0; i < 4; i++)
        {
            int xx = t.x + dir[i][0];
            int yy = t.y + dir[i][1];
            if (!vis[xx][yy]&&check(xx,yy))
            {
                cnt++;
                vis[xx][yy] = 1;
                q.push({ xx,yy });
            }
        }
    }
}

int main()
{
    PII s;
    while (true)
    {
        cin >> m >> n; if (m == 0 && n == 0)return 0;
        for (int i = 0; i < n; i++)
        {
            scanf("%s", g[i]);
            for (int j = 0; j < m; j++)if (g[i][j] == '@')s = { i,j };
        }

        memset(vis, 0, sizeof(vis));
        bfs(s);
        cout << cnt << endl;
    }



}