poj 1979 [ BFS 32ms 数据范围的事，可能造成 dfs 比 bfs 快了！ ]

#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <vector>
#include <stack>
#include <deque>
#include <queue>
#include <bitset>
#include <list>
#include <map>
#include <set>
#include <iterator>
#include <algorithm>
#include <functional>
#include <utility>
#include <sstream>
#include <climits>
#include <cassert>
#define MID(x,y) ( ( x + y ) >> 1 )
#define L(x) ( x << 1 )
#define R(x) ( x << 1 | 1 )
#define BUG puts("here!!!");
#define STOP system("pause");

using namespace std;
const int N = 25;

string mat[N];

struct Point {
	int x, y;
};
int n, m, ans;
int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, 1, -1};
bool ok(int i, int j) {
	return (i >= 0 && i < n && j >= 0 && j < m && mat[i][j] != '#');
}
queue<Point> Q;
Point you;
void bfs() {
	Point nex;
	Q.push(you);
	ans = 1;
	while(!Q.empty()) {
		Point t = Q.front();
		Q.pop();
		for(int i = 0; i < 4; i++) {
			nex.x = t.x + dx[i];
			nex.y = t.y + dy[i];
			if(ok(nex.x, nex.y)) {
				mat[nex.x][nex.y] = '#';
				++ans;
				Q.push(nex);
			}
		}
	}
	cout << ans << endl;
}
int main() {
	while(cin >> m >> n, m | n) {
		for(int i = 0; i < n; i++) {
			cin >> mat[i];
			for(int j = 0; j < m; j++) {
				if(mat[i][j] == '@') {
					you.x = i;
					you.y = j;
					mat[i][j] = '#';
					break;
				}
			}
		}
		bfs();
	}
	return 0;
}