HDU1312：Red and Black

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int n,m,ans;
char map[25][25];
int yi[4][2]={{1,0},{-1,0},{0,1},{0,-1}};
void dfs(int x,int y)
{
    int i,rx,ry;
    map[x][y]=‘#‘;
    ans++;
    for (i=0;i<4;i++)
    {
        rx=x+yi[i][0];
        ry=y+yi[i][1];
        if (rx>=1&&rx<=n&&ry>=1&&ry<=m&&map[rx][ry]==‘.‘)
        {
            dfs(rx,ry);
        }
    }
}
int main()
{
    int i,j,x,y;
    while (~scanf("%d%d",&m,&n))
    {
        if (n==0&&m==0) break;
        ans=0;
        for (i=1;i<=n;i++)
        for (j=1;j<=m;j++)
        {
            scanf(" %c",&map[i][j]);
            if (map[i][j]==‘@‘)
            {
                x=i;
                y=j;
            }
        }
        dfs(x,y);
        printf("%d\n",ans);
    }
    return 0;
}