其实这个题不需要用vis数组，访问过的直接用'*'把'#'填了就好了

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

int m, n;
char mp[105][105];
vector<vector<int>> direction {{-1, 0}, {-1, 1}, {0, 1}, {1, 1}, {1, 0}, {1, -1}, {0, -1}, {-1, -1}};
int ans;

void dfs(int x, int y) {
	if(mp[x][y] == '*' || !mp[x][y])
		return;
	//用*把#给填了
	mp[x][y] = '*';
		
	for(int i = 0; i < 8; i++) {
		int nx = x + direction[i][0];
		int ny = y + direction[i][1];
		dfs(nx, ny);
	}
}

int main()
{
	while(cin >> m >> n) {
		if(m == 0 && n == 0)
			break;
			
		ans = 0;
		memset(mp, 0, sizeof(mp));
		
		for(int i = 1; i <= m; i++) {
			string s;
			cin >> s;
			for(int j = 1; j <= n; j++) {
				mp[i][j] = s[j-1];
			}
		}
		//把每个点都访问一遍，被访问过的都用'*'填上了
		for(int i = 1; i <= m; i++)
			for(int j = 1; j <= n; j++)
				if(mp[i][j] == '@') {
					dfs(i, j);
					++ans;
				}
		cout << ans << endl;		
...