广搜

Problem Description

There is a rectangular room, covered with square tiles. Each tile is colored either red or black. A man is standing on a black tile. From a tile, he can move to one of four adjacent tiles. But he can't move on red tiles, he can move only on black tiles.

Write a program to count the number of black tiles which he can reach by repeating the moves described above. 

 

 

Input

The input consists of multiple data sets. A data set starts with a line containing two positive integers W and H; W and H are the numbers of tiles in the x- and y- directions, respectively. W and H are not more than 20.

There are H more lines in the data set, each of which includes W characters. Each character represents the color of a tile as follows.

'.' - a black tile 
'#' - a red tile 
'@' - a man on a black tile(appears exactly once in a data set) 

 

 

Output

For each data set, your program should output a line which contains the number of tiles he can reach from the initial tile (including itself).

#include 
#include 
#include 
using namespace std;
const int maxn=30;
int n,m,ans;
char map[maxn][maxn];  //地图
bool vis[maxn][maxn];  //判重
int dir[4][2]= {{1,0},{-1,0},{0,1},{0,-1}};//4个方向
int qx[maxn*maxn],qy[maxn*maxn];
void bfs(int x,int y)
    {
        int l=0,r=0;
        qx[r]=x,qy[r++]=y;
        vis[x][y]=1;
        ans++;   //统计
        while(l=1&&nx<=n&&ny>=1&&ny<=m&&!vis[nx][ny]&&map[nx][ny]!='#')//边界条件
                {
                    ans++;
                    vis[nx][ny]=1;
                    qx[r]=nx,qy[r++]=ny;
                }
            }
        }
   }
int main()
{
     while(scanf("%d%d",&m,&n)==2&&(n||m))
    {
        int sx,sy;
        for(int i=1; i<=n; i++)
            for(int j=1; j<=m; j++)
            {
                cin>>map[i][j];
                if(map[i][j]=='@') sx=i,sy=j;//初始点
            }
        ans=0;
        memset(vis,0,sizeof(vis));
        bfs(sx,sy);
        printf("%d\n",ans);
    }
    return 0;
}