【费用流】bzoj3280 小R的烦恼

类似bzoj1221 http://www.cnblogs.com/autsky-jadek/p/4174087.html

只不过大学有多个，所以我们另开一个节点汇总所有'S->大学'的边，然后再把这个节点和Yi相连即可。

死于初始化。

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<queue>
using namespace std;
#define MAXN 161
#define MAXM 40001
#define INF 2147483647
int S,T,Hos;
int N,M,K,sum;
int en,u[MAXM],v[MAXM],first[MAXN],next[MAXM],cap[MAXM],cost[MAXM];//Next Array
bool inq[MAXN];
int d[MAXN]/*spfa*/,p[MAXN]/*spfa*/,a[MAXN]/*可改进量*/;
queue<int>q;
void Init_MCMF()
{
    memset(p,0,sizeof(p));
    memset(a,0,sizeof(a));
    memset(first,-1,sizeof(first));
    memset(next,0,sizeof(next));
    memset(u,0,sizeof(u));
    memset(v,0,sizeof(v));
    memset(cap,0,sizeof(cap));
    memset(cost,0,sizeof(cost));
    en=0;S=0;T=(N<<1)+M+2;Hos=T-1;sum=0;
}
void AddEdge(const int &U,const int &V,const int &W,const int &C)
{u[en]=U; v[en]=V; cap[en]=W; cost[en]=C; next[en]=first[U]; first[U]=en++;
u[en]=V; v[en]=U; cost[en]=-C; next[en]=first[V]; first[V]=en++;}
bool Spfa(int &Flow,int &Cost)
{
    memset(d,0x7f,sizeof(d));
    memset(inq,0,sizeof(inq));
    d[S]=0; inq[S]=1; p[S]=0; a[S]=INF; q.push(S);
    while(!q.empty())
      {
        int U=q.front(); q.pop(); inq[U]=0;
        for(int i=first[U];i!=-1;i=next[i])
          if(cap[i] && d[v[i]]>d[U]+cost[i])
            {
              d[v[i]]=d[U]+cost[i];
              p[v[i]]=i;
              a[v[i]]=min(a[U],cap[i]);
              if(!inq[v[i]]) {q.push(v[i]); inq[v[i]]=1;}
            }
      }
    if(d[T]>2100000000) return 0;
    Flow+=a[T]; Cost+=d[T]*a[T]; int U=T;
    while(U!=S)
      {
        cap[p[U]]-=a[T]; cap[p[U]^1]+=a[T];
        U=u[p[U]];
      }
    return 1;
}
int Mincost()
{
    int Flow=0,Cost=0;
    while(Spfa(Flow,Cost));
    if(Flow<sum) puts("impossible");
    else printf("%d
",Cost);
}
int A[51],B,C,D[51],E[51],zu;
int main()
{
	scanf("%d",&zu);
	for(int Z=1;Z<=zu;++Z)
	  {
	  	printf("Case %d: ",Z);
	  	scanf("%d%d%d",&N,&M,&K);
	    Init_MCMF();
	    for(int i=1;i<=N;++i) scanf("%d",&A[i]),sum+=A[i];
    	for(int i=1;i<=M;++i)
		  {
		  	scanf("%d%d",&B,&C);
		    AddEdge(S,i+(N<<1),B,C);
			AddEdge(i+(N<<1),Hos,INF,0);
		  }
    	for(int i=1;i<=K;++i) scanf("%d%d",&D[i],&E[i]);
    	for(int i=1;i<=N;++i)
    	  {
    	  	AddEdge(S,i,A[i],0);
            AddEdge(i+N,T,A[i],0);
            AddEdge(Hos,i+N,INF,0);
            if(i+1<=N) AddEdge(i,i+1,INF,0);
            for(int j=1;j<=K;++j)
              if(i+D[j]+1<=N)
                AddEdge(i,i+D[j]+1+N,INF,E[j]);
    	  }
    	Mincost();
	  }
	return 0;
}