嗯...

 

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1312

 

一道很经典的dfs，设置上下左右四个方向，读入时记下起点，然后跑dfs即可...最后答案加上起点的1，无需回溯！！

 

AC代码：

1 #include
      
        2 #include
       
         3 #include
        
          4  5 using namespace std; 6  7 int dir[4][2] = {
    {-1, 0}, {
    1, 0}, {
    0, -1}, {
    0, 1}}; 8  9 int n, m, ans;10 bool flag[25][25];11 char g[25][25];12 13 inline void dfs(int x, int y){14     for(int i = 0; i < 4; i++){15         int nx = x + dir[i][0];16         int ny = y + dir[i][1];17         if(nx <= m && ny <= n && nx > 0 && ny > 0 && !flag[nx][ny] && g[nx][ny] == '.'){18             ans++;19             flag[nx][ny] = 1;20             dfs(nx, ny);21         }22     }23 }24 25 int main(){26     while(~scanf("%d%d", &n, &m) && n != 0 && m != 0){27         int x, y;28         memset(flag, 0, sizeof(flag));29         for(int i = 1; i <= m; i++){30             for(int j = 1; j <= n; j++){31                 cin >> g[i][j];32                 if(g[i][j] == '@'){ x = i; y = j;}33             }34         }35         ans = 0;36         flag[x][y] = 1;37         dfs(x, y);38         printf("%d\n", ans + 1);39     }40     return 0;41 }42