关于读入

1. 对于结尾是0 0 才停止读入的数据，可以这样读入while(cin >> m >> n, n || m)
2. bfs写了一下。

#include<bits/stdc++.h>
using namespace std;
typedef pair<int,int> PII;
#define x first
#define y second
const int N = 30, M = N * N;
PII q[M];
char g[N][N];
bool st[N][N];
int n, m;

int bfs(int sx, int sy){
    int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
    int hh = 0, tt = 0;
    q[0] = {sx, sy};
    st[sx][sy] = true;
    int cnt =1;

    while( hh <= tt){
        auto t = q[ hh ++];
        for(int i = 0; i < 4; i ++){
            int a = t.x + dx[i], b = t.y + dy[i];
            if( a < 0 || a >= n || b < 0 || b >= m || st[a][b] || g[a][b] == '#') continue;
            cnt ++;
            st[a][b] = true;
            q[++ tt] = {a,b};

        }
    }
    return cnt;
}


int main(){
    while(cin >> m >> n, n || m){
        memset(st, 0, sizeof st);
        for(int i = 0; i< n ;i ++) cin >> g[i];
        for(int i = 0; i < n; i ++)
            for(int j = 0; j< m; j ++)
                if( g[i][j] == '@'){
                    cout << bfs(i ,j) << endl;
                }
    }
}