bzoj1711

题解：

原点->食物建一个1

食物->牛见一个1

牛->牛'见一个1

牛'->饮料1

饮料->汇点1

代码：

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
const int N=405;
int q[N*N],n,m,sum,dis[N],k,d,x,y,ans,f[N],z,a[N][N];
int bfs()
{
    memset(dis,0xff,sizeof dis);
    dis[1]=0;
    int l=0,r=1;
    q[1]=1;
    while (l<r)
     {
         int j=q[++l];
         for (int i=1;i<=n;i++)
          if (dis[i]<0&&a[j][i]>0)
           {
               dis[i]=dis[j]+1;
               q[++r]=i;
           }
     }
    if (dis[n]>0)return 1;
    return 0; 
}
int find(int x,int low)
{
    int b=0;
    if (x==n)return low;
    for (int i=1;i<=n;i++)
     if (a[x][i]>0&&dis[i]==dis[x]+1&&(b=find(i,min(low,a[x][i]))))
      {
          a[x][i]-=b;
          a[i][x]+=b;
          return b;
      }
    return 0;  
}
int main()
{
    scanf("%d%d%d",&n,&m,&k);
    memset(a,0,sizeof a);
    for (int i=1;i<=n;i++)a[i+m+1][i+m+n+1]=1;
    for (int i=1;i<=n;i++)
     {
         scanf("%d%d",&x,&y);
         while (x--)
          {
              scanf("%d",&d);
              a[1][d+1]=a[d+1][i+m+1]=1;
          }
         while (y--)
         {
             scanf("%d",&d);
             a[d+2*n+m+1][2*n+m+k+2]=a[i+m+n+1][d+2*n+m+1]=1;
         } 
     }
    n=n*2+m+k+2; 
    ans=0;int t; 
    while (bfs())
     while (t=find(1,0x7fffffff))ans+=t;
    printf("%d
",ans); 
}