poj 3281 Dining

http://poj.org/problem?id=3281

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <queue>
#include <algorithm>
using namespace std;

const int MAX=0x7fffffff;
const int N=510;
int path[N][N];
int l[N];
int n,f,d;
int Bfs()
{
   memset(l,-1,sizeof(l));
   queue< int >str;
   str.push(0);
   int k;
   l[0]=0;
   while(!str.empty())
   {
       k=str.front();
       str.pop();
       for(int i=n;i>=0;--i)
       { if(path[k][i]>0&&l[i]==-1)
           {
               l[i]=l[k]+1;
               str.push(i);
           }
       }
   }
   //for(int i=0;i<=n;++i)
   //printf("( %d  %d ) ",i,l[i]);
   //cout<<endl;
   if(l[n]!=-1)
   return true;
   return false;
}
int Dfs(int x,int Max)
{
    int sum=Max;
    if(x==n)
    {return Max;}
    for(int i=0;i<=n;++i)
    {
        if(sum==0)
        break;
        if(l[i]==l[x]+1&&path[x][i]>0)
        {
            int w=Dfs(i,min(sum,path[x][i]));
            path[x][i]-=w;
            path[i][x]+=w;
            sum-=w;
        }
    }
    return (Max-sum);
}
int main()
{
    //freopen("data.txt","r",stdin);
    //while(1)
    {
    scanf("%d %d %d",&n,&f,&d);
    int k1,k2;
    int w;
    memset(path,0,sizeof(path));
    for(int i=1;i<=n;++i)
    {
        path[i][i+n]=1;
        scanf("%d %d",&k1,&k2);//cout<<i<<" "<<i+n<<endl;
        while(k1--)
        {
           scanf("%d",&w);
           path[w+2*n][i]=1;//cout<<w+2*n<<" "<<i<<endl;
           path[0][w+2*n]=1;
        }
        while(k2--)
        {
            scanf("%d",&w);
            path[i+n][w+2*n+f]=1;//cout<<i+n<<" "<<w+2*n+f<<endl;
            path[w+2*n+f][2*n+f+d+1]=1;
        }
    }
    n=2*n+f+d+1;//cout<<"n=== "<<n<<endl;
    int ans=0;
    while(Bfs())
    {
        while(1)
        {
            w=Dfs(0,MAX);
            if(w==0)
            break;
            ans+=w;
        }

    }
    printf("%d\n",ans);
    }
    return 0;
}