BZOJ3876: [Ahoi2014]支线剧情

建图 等下整理到网络流学习笔记里去

有上下界的网络流

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<queue>
using namespace std;


struct Chain
{
    int u,flow,cost;
    Chain *next,*Pair;
}*Head[100001];

int S,T;

inline void Add(int  u,int v,int flow,int cost)
{
    Chain *tp=new Chain;
    tp->next=Head[u];
    tp->u=v,tp->flow=flow,tp->cost=cost;
    Head[u]=tp;
    tp=new Chain;
    tp->next=Head[v];
    tp->u=u,tp->flow=0,tp->cost=-cost;
    Head[v]=tp;
    Head[v]->Pair=Head[u];
    Head[u]->Pair=Head[v];
}

Chain *Pre[100001];
int Dis[100001],flow[100001];
queue<int>Q;
bool V[100001];
int ans;
const
  int INF=1<<29;
  int Mf;
inline bool SPFA(int S,int T)
{
    memset(Dis,-1,sizeof(Dis));
    Dis[S]=0;
    V[S]=true;
    Q.push(S);
    flow[S]=INF;
    while(!Q.empty())
    {
        int u=Q.front();
        for(Chain *tp=Head[u];tp;tp=tp->next)
          if(tp->flow&&(Dis[tp->u]==-1||Dis[tp->u]>Dis[u]+tp->cost))
          {
            Dis[tp->u]=Dis[u]+tp->cost;
            Pre[tp->u]=tp;
            flow[tp->u]=min(tp->flow,flow[u]);
            if(!V[tp->u])
              Q.push(tp->u),V[tp->u]=true;
          }
        V[u]=false;
        Q.pop();
    }
    if(Dis[T]==-1)return false;
    ans+=Dis[T]*flow[T];
    int f=flow[T];
    Mf+=f;
    int t=T;
    while(t^S)
    {
        Pre[t]->flow-=f,Pre[t]->Pair->flow+=f;
        t=Pre[t]->Pair->u;
    }
    return true;
}


int Du[10001];
char c;
inline void read(int &a)
{
    a=0;do c=getchar();while(c<'0'||c>'9');
    while(c<='9'&&c>='0')a=(a<<3)+(a<<1)+c-'0',c=getchar();
}
int st,ed;
int main()
{
     int i,j,k,t,n,L;
     read(n);
     S=n+1,T=n+2,st=1,ed=0;
     for(i=1;i<=n;i++)
      {
         read(k);
         Add(i,T,k,0);
         if(i^1)Add(i,1,INF,0);
         for(j=1;j<=k;j++)
           {
            read(t),read(L);
            Add(S,t,1,L);       
            Add(i,t,INF,L);    
           }
      }
    while(SPFA(S,T));
    printf("%d\n",ans);
    return 0;
}