hdu4185

题解：
每两个联通的油井建边

然后二分图最大匹配

最后答案除以2

代码：

#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=;
char c;
int T,a[N/][N/],f[N],match[N],fi[N],cas,num,ne[N],zz[N],n,cnt;
int dfs(int x)
{
    for (int i=fi[x];i;i=ne[i])
     if (!f[zz[i]])
      {
          f[zz[i]]=;
          if (!match[zz[i]]||dfs(match[zz[i]]))
           {
               match[zz[i]]=x;
               return ;
           }
      }
    return ;
}
void jb(int x,int y)
{
    ne[++num]=fi[x];
    fi[x]=num;
    zz[num]=y;
    ne[++num]=fi[y];
    fi[y]=num;
    zz[num]=x;
}
int main()
{
    scanf("%d",&T);
    while (T--)
     {
         memset(a,,sizeof a);
         memset(fi,,sizeof fi);
         num=;
         scanf("%d",&n);
         for (int i=;i<n;i++)
          for (int j=;j<n;j++)
           {
               int ch=getchar();
               while (ch!='.'&&ch!='#')ch=getchar();
               if (ch=='#')a[i][j]=++cnt;
               else a[i][j]=;
           }
         for (int i=;i<n;i++)
         for (int j=;j<n;j++)
          if (a[i][j])
           {
               if (a[i+][j])jb(a[i][j],a[i+][j]);
               if (a[i][j+])jb(a[i][j],a[i][j+]);
           }
        int ans=;
        for (int i=;i<=cnt;i++)
         {
             memset(f,,sizeof f);
             ans+=dfs(i);
         }
        printf("Case %d: %d\n",++cas,ans/);
     }
    return ;
}