poj-3281【最大流】

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转换成最大流求解，刚开始看最大流，留着当模板#include <cstring>#include <cstdio>#include <iostream>#include <algorithm>#include <queue>#include <vector>#include <string>#include <cmath>#define maxn 20#define Max 0x3f3f3f3fusing namespace std;struct node{    int to;    int value;    int pos;};vector<node>G[405];bool used[405];int leve[405];int lazy[405];void addnode(int from,int to,int val){    G[from].push_back((node){to,val,G[to].size()});    G[to].push_back((node){from,0,G[from].size()-1});}int bfs(int s){    memset(leve,-1,sizeof(leve));    leve[s]=0;    queue<int>que;    que.push(s);    while(!que.empty())    {        int now=que.front();        que.pop();        for (int i=0;i<G[now].size();i++)        {            node &tag=G[now][i];            if (tag.value>0&&leve[tag.to]<0)            {                leve[tag.to]=leve[now]+1;                que.push(tag.to);            }        }    }}int dfs(int v,int t,int f){    if (v==t)return f;    for (int & i=lazy[v];i<G[v].size();i++)    {        node & now=G[v][i];        if (now.value>0&&leve[v]<leve[now.to])        {            int tag=dfs(now.to,t,min(f,now.value));            if (tag>0)            {                now.value-=tag;                G[now.to][now.pos].value+=tag;                return tag;            }        }    }    return 0;}int Maxflow(int s,int t){    int flow=0;    for(;;)    {        bfs(s);        if (leve[t]<0)        {            return flow;        }        int f;        memset(lazy,0,sizeof(lazy));        while((f=dfs(s,t,Max))>0)        {            flow+=f;        }    }}int main(){    int n,k,d;    int a,b,c,all;    while(scanf("%d %d %d",&n,&k,&d)!=EOF)    {        all=n+k+d+n+1;        for (int i=0;i<405;i++)        {            G[i].clear();        }        for (int i=1;i<=k;i++)//食物跟源点连边        {            addnode(0,i,1);        }        for (int i=1;i<=n;i++)//牛连边        {            addnode(k+i,k+i+n,1);        }        for (int i=1;i<=d;i++)        {            addnode(k+n+n+i,all,1);        }        for (int i=1;i<=n;i++)        {            scanf("%d %d",&a,&b);            while(a--)            {                scanf("%d",&c);                addnode(c,k+i,1);            }            while(b--)            {                scanf("%d",&c);                addnode(k+n+i,k+2*n+c,1);            }        }        int num=Maxflow(0,all);        printf("%d\n",num);    }    return 0;}
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