题目链接:http://poj.org/problem?id=1149
题目思路:主要就是建图问题,推荐论文:https://wenku.baidu.com/view/0ad00abec77da26925c5b01c.html
剩下的就是网络流的模板问题了
AC代码
#include<queue>
#include<cstring>
#include<iostream>
#include<set>
#include<stdio.h>
using namespace std;
#define maxn 200
#define maxm 100000
#define inf 0x3f3f3f3f
int first[maxn];
int edge_num;
int lev[maxn];
int vis[maxn];
int mark[1200];
int num[1200];
struct edge{
int u,v;
int cap;
int next;
}e[maxm];
void add_edge(int u,int v,int c)
{
e[edge_num].u=u;
e[edge_num].v=v;
e[edge_num].cap=c;
e[edge_num].next=first[u];
first[u]=edge_num++;
e[edge_num].u=v;
e[edge_num].v=u;
e[edge_num].cap=0;
e[edge_num].next=first[v];
first[v]=edge_num++;
}
int Dinic_spath(int s,int t)
{
queue<int>q;
q.push(s);
memset(lev,-1,sizeof(lev));
memset(vis,0,sizeof(vis));
lev[s]=0;
while(!q.empty())
{
int u=q.front();
vis[u]=0;
q.pop();
for(int k=first[u];k!=-1;k=e[k].next)
{
int v=e[k].v;
if(lev[v]==-1&&e[k].cap>0)
{
lev[v]=lev[u]+1;
if(!vis[v])
{
vis[v]=1;
q.push(v);
}
}
}
}
return lev[t]!=-1;
}
int Dinic_dfs(int u,int t,int flow)
{
int cost=0;
if(u==t) return flow;
for(int k=first[u];k!=-1;k=e[k].next)
{
int v=e[k].v;
if(lev[v]==lev[u]+1&&e[k].cap>0)
{
int minn=Dinic_dfs(v,t,min(e[k].cap,flow-cost));
if(minn>0)
{
e[k].cap=e[k].cap-minn;
e[k^1].cap=e[k^1].cap+minn;
cost+=minn;
if(cost==flow) break;
}
else
lev[v]=-1;
}
}
return cost;
}
int main()
{
memset(first,-1,sizeof(first));
edge_num=0;
memset(mark,0,sizeof(mark));
int M,N;
scanf("%d%d",&M,&N);
for(int i=1;i<=M;++i)
scanf("%d",&num[i]);
for(int i=1;i<=N;++i)
{
set<int>sets;
int temp;
scanf("%d",&temp);
int temp2=0;
for(int j=1;j<=temp;++j)
{
int x;
scanf("%d",&x);
if(mark[x]==0)
{
mark[x]=i;
temp2+=num[x];
}
else
sets.insert(mark[x]);
}
scanf("%d",&temp);
add_edge(i,N+1,temp);
add_edge(0,i,temp2);
for(set<int>::iterator pi=sets.begin();pi!=sets.end();++pi)
add_edge(*pi,i,inf);
sets.clear();
}
int f=0;
while(Dinic_spath(0,N+1))
f+=Dinic_dfs(0,N+1,inf);
printf("%d\n",f);
return 0;
}