bzoj 1834: [ZJOI2010]network 网络扩容

 #include<cstdio>
 #include<iostream>
 #include<cstring>
 #define M 100000
 #define inf 2139062143
 using namespace std;
 struct data
 {
     int l,r,w;
 }a[M];
 int q[M],d[M],head[M],next[*M],u[*M],v[*M],cnt=,n,m,K,ans;
 int cnt1=,head1[M],next1[*M],fro[*M],u1[*M],v1[*M],w1[*M],f[M],fr[M];
 void jia(int a1,int a2,int a3)
 {
     cnt++;
     u[cnt]=a2;
     v[cnt]=a3;
     next[cnt]=head[a1];
     head[a1]=cnt;
 }
 void jia1(int a1,int a2,int a3,int a4)
 {
     cnt1++;
     fro[cnt1]=a1;
     u1[cnt1]=a2;
     v1[cnt1]=a3;
     w1[cnt1]=a4;
     next1[cnt1]=head1[a1];
     head1[a1]=cnt1;
 }
 bool bfs()
 {
     memset(d,,sizeof(int)*(*n));
     int h=,t=;
     q[]=;
     d[]=;
     for(;h<t;)
       {
         h++;
         int p=q[h];
         for(int i=head[p];i;i=next[i])
           if(!d[u[i]]&&v[i])
             {
                 d[u[i]]=d[p]+;
                 if(d[n])
                   return ;
                 t++;
                 q[t]=u[i];
             }
       }
     return ;
 }
 int dinic(int s,int f)
 {
     if(s==n)
       return f;
     int rest=f;
     for(int i=head[s];i&&rest;i=next[i])
       if(v[i]&&d[u[i]]==d[s]+)
         {
             int now=dinic(u[i],min(rest,v[i]));
             if(!now)
               d[u[i]]=;
             v[i]-=now;
             v[i^]+=now;
             rest-=now;
         }
     return f-rest;
 }
 bool spfa()
 {
     memset(d,,sizeof(int)*(*n));
     d[]=;
     f[]=;
     q[]=;
     int h=,t=;
     for(;h<t;)
       {
         h++;
         int p=q[h];
         f[p]=;
         for(int i=head1[p];i;i=next1[i])
           if(v1[i]&&d[u1[i]]>d[p]+w1[i])
             {
                 d[u1[i]]=d[p]+w1[i];
                 fr[u1[i]]=i;
                 if(!f[u1[i]])
                   {
                     f[u1[i]]=;
                     t++;
                     q[t]=u1[i];
                     }
             }
       }
     if(d[n]!=inf)
       return ;
     return ;
 }
 void mcf()
 {
     int mx=inf;
     for(int i=fr[n];i;i=fr[fro[i]])
       mx=min(mx,v1[i]);
     for(int i=fr[n];i;i=fr[fro[i]])
       {
         v1[i]-=mx;
         v1[i^]+=mx;
         ans+=mx*(w1[i]);
       }
 }
 int main()
 {
     scanf("%d%d%d",&n,&m,&K);
     for(int i=;i<=m;i++)
       {
         int a3;
         scanf("%d%d%d%d",&a[i].l,&a[i].r,&a3,&a[i].w);
         jia(a[i].l,a[i].r,a3);
         jia(a[i].r,a[i].l,);
       }
     for(;bfs();)
       ans+=dinic(,inf);
     printf("%d ",ans);
     for(int i=;i<=cnt;i+=)
       {
         jia1(a[i/].l,a[i/].r,inf,a[i/].w);
         jia1(a[i/].r,a[i/].l,,-a[i/].w);
         jia1(a[i/].l,a[i/].r,v[i],);
         jia1(a[i/].r,a[i/].l,v[i+],);
       }
     jia1(,,K,);
     jia1(,,,);
     ans=;
     for(;spfa();)
       mcf();
     printf("%d\n",ans);
     return ;
 }

一遍最大流，一遍费用流。第一问跑完之后在残余网络建边，单位费用为扩容费用，