【网络流#7】POJ 3281 Dining 最大流 - 《挑战程序设计竞赛》例题

#include<cstdio>
#include<cstring>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<set>
#include<map>
#include<stack>
#include<vector>
#include<queue>
#include<string>
#include<sstream>
#define eps 1e-9
#define ALL(x) x.begin(),x.end()
#define INS(x) inserter(x,x.begin())
#define FOR(i,j,k) for(int i=j;i<=k;i++)
#define MAXN 1005
#define MAXM 30005
using namespace std;
typedef long long LL;
int i,j,k,n,m,x,y,T,ans,big,cas,F,D,S,f,d,id;
bool flag;

const int inf = 0x3f3f3f3f;
struct edgenode
{
    int from,to,next;
    int cap;
}edge[MAXM];
int Edge,head[MAXN],ps[MAXN],dep[MAXN];

void add_edge(int x,int y,int c)
{
    edge[Edge].from=x;
    edge[Edge].to=y;
    edge[Edge].cap=c;
    edge[Edge].next=head[x];
    head[x]=Edge++;
    
    edge[Edge].from=y;
    edge[Edge].to=x;
    edge[Edge].cap=0;
    edge[Edge].next=head[y];
    head[y]=Edge++;
}

int dinic(int n,int s,int t)
{
    int tr,flow=0;
    int i,j,k,l,r,top;
    while(1){
        memset(dep,-1,(n+1)*sizeof(int));
        for(l=dep[ps[0]=s]=0,r=1;l!=r;)//BFS部分，将给定图分层 
        {
            for(i=ps[l++],j=head[i];j!=-1;j=edge[j].next)
            {
                if (edge[j].cap&&-1==dep[k=edge[j].to])
                {
                    dep[k]=dep[i]+1;ps[r++]=k;
                    if(k==t)
                    {
                        l=r;
                        break;
                    }
                }
            }
        }
        if(dep[t]==-1)break;
        
        for(i=s,top=0;;)//DFS部分 
        {
            if(i==t)//当前点就是汇点时 
            {
                for(k=0,tr=inf;k<top;++k)
                    if(edge[ps[k]].cap<tr)tr=edge[ps[l=k]].cap;
                    
                for(k=0;k<top;++k)
                    edge[ps[k]].cap-=tr,edge[ps[k]^1].cap+=tr;
                    
                flow+=tr;
                i=edge[ps[top=l]].from;
            }
            
            for(j=head[i];j!=-1;j=edge[j].next)//找当前点所指向的点 
                if(edge[j].cap&&dep[i]+1==dep[edge[j].to]) break;
                
            if(j!=-1)
            {
                ps[top++]=j;//当前点有所指向的点，把这个点加入栈中 
                i=edge[j].to;
            }
            else
            { 
                if (!top) break;//当前点没有指向的点，回溯 
                dep[i]=-1;
                i=edge[ps[--top]].from;
            }
        }
    }
    return flow;
}


int main()
{
    memset(head,-1,sizeof(head));Edge=0;
    scanf("%d%d%d",&n,&F,&D);
    S=0;
    T=n+n+F+D+1;
    for (i=1;i<=F;i++)
    {
        add_edge(S,2*n+i,1);
    }
    for (i=1;i<=D;i++)
    {
        add_edge(2*n+F+i,T,1);
    }
    
    for (i=1;i<=n;i++)
    {
        scanf("%d%d",&f,&d);
        add_edge(i,n+i,1);
        for (j=1;j<=f;j++)
        {
            scanf("%d",&id);
            id=2*n+id; 
            add_edge(id,i,1);
        }
        for (j=1;j<=d;j++)
        {
            scanf("%d",&id);
            id=2*n+F+id;
            add_edge(n+i,id,1);
        }
    }
    printf("%d\n",dinic(T+1,S,T));
    return 0;
}