poj 1149 pigs ---- 最大流

　　题意以及分析：http://ycool.com/post/zhhrrm6#rule3

　　主要是建图，简化图，然后在套最大流的模板。

#include <iostream>
#include<string.h>
#include<cstdio>
using namespace std;

struct Node
{
    int v,cap,flow,next;

    Node(){}
    Node(int _v,int _cap,int _flow,int _next)
    {
        v=_v;
        cap=_cap;
        flow=_flow;
        next=_next;
    }
};

const int INF=;
Node edges[];
int pig[],a[][];
int n,m,s,t,head[],e;

void Add(int u,int v,int cap)
{
    edges[e]=Node(v,cap,,head[u]);
    head[u]=e++;
    edges[e]=Node(u,,,head[v]);
    head[v]=e++;
}

int num[],h[],curedge[],pre[];

int Maxflow(int s,int t,int n)
{
    int ans=,i,k,x,d,u;

    memset(num,,sizeof(num));
    memset(h,,sizeof(h));
    for(i=;i<=n;i++) curedge[i]=head[i];
    num[n]=n;u=s;
    while(h[u]<n)
    {
        if(u==t)
        {
            d=INF+;
            for(i=s;i!=t;i=edges[curedge[i]].v) if(d>edges[curedge[i]].cap)
                k=i,d=edges[curedge[i]].cap;
            for(i=s;i!=t;i=edges[curedge[i]].v)
            {
                x=curedge[i];
                edges[x].cap-=d;
                edges[x].flow+=d;
                edges[x^].cap+=d;
                edges[x^].flow-=d;
            }
            ans+=d;u=k;
        }
        for(i=curedge[u];i!=-;i=edges[i].next) if(edges[i].cap>&&h[u]==h[edges[i].v]+)
            break;
        if(i!=-)
        {
            curedge[u]=i;
            pre[edges[i].v]=u;
            u=edges[i].v;
        }
        else
        {
            if(--num[h[u]]==) break;
            curedge[u]=head[u];
            for(x=n,i=head[u];i!=-;i=edges[i].next) if(edges[i].cap>&&h[edges[i].v]<x)
                x=h[edges[i].v];
            h[u]=x+;num[h[u]]++;
            if(u!=s) u=pre[u];
        }
    }
    return ans;
}

int main()
{
    while(scanf("%d%d",&m,&n)!=EOF)
    {
        int i,j,x,p,num;

        s=;t=n+;
        memset(head,-,sizeof(head));
        e=;
        for(i=;i<=m;i++) scanf("%d",&pig[i]);
        for(i=;i<=m;i++) a[i][]=;
        for(i=;i<=n;i++)
        {
            scanf("%d",&x);
            while(x--) scanf("%d",&p),a[p][++a[p][]]=i;
            scanf("%d",&num);
            Add(i,t,num);
        }
        for(i=;i<=m;i++) if(a[i][]) Add(s,a[i][],pig[i]);
        for(i=;i<=m;i++) for(j=;j<a[i][];j++) Add(a[i][j],a[i][j+],INF);
        printf("%d\n",Maxflow(s,t,t));
    }
    return ;
}