bzoj 3130: [Sdoi2013]费用流

 #include<cstdio>
 #include<iostream>
 #define M 10000
 #define inf 0x7fffffff
 #include<cstring>
 #define eps 1e-5
 using namespace std;
 struct data
 {
     int x,y;
     double z;
 }a[M];
 int d[M],q[M],S,T,cnt=,n,m,head[M],next[M],u[M];
 double p,w[M],l,r,ss,ans,ans1;
 void jia1(int a1,int a2,double a3)
 {
     cnt++;
     next[cnt]=head[a1];
     head[a1]=cnt;
     u[cnt]=a2;
     w[cnt]=a3;
     return;
 }
 void jia(int a1,int a2,double a3)
 {
     jia1(a1,a2,a3);
     jia1(a2,a1,);
     return;
 }
 bool bfs()
 {
     memset(d,,sizeof(int)*(T+));
     int h=,t=;
     q[]=S;
     d[S]=;
     for(;h<t;)
       {
         h++;
         int p=q[h];
         for(int i=head[p];i;i=next[i])
           if(!d[u[i]]&&w[i])
             {
                 d[u[i]]=d[p]+;
                 if(d[T])
                   return ;
                 t++;
                 q[t]=u[i];
             }
       }
     return ;
 }
 double dinic(int s,double f)
 {
     if(s==T)
       return f;
     double rest=f;
     for(int i=head[s];i&&rest;i=next[i])
       if(w[i]&&d[u[i]]==d[s]+)
         {
             double now=dinic(u[i],min(rest,w[i]));
             if(!now)
               d[u[i]]=;
             w[i]-=now;
             w[i^]+=now;
             rest-=now;
         }
     return f-rest;
 }
 void jian(double mi)
 {
     cnt=;
     memset(head,,sizeof(int)*(T+));
     for(int i=;i<=m;i++)
       if(a[i].z<mi)
         jia(a[i].x,a[i].y,a[i].z);
       else
         jia(a[i].x,a[i].y,mi);
     return;
 }
 int main()
 {
     scanf("%d%d%lf",&n,&m,&p);
     for(int i=;i<=m;i++)
       {
         scanf("%d%d%lf",&a[i].x,&a[i].y,&a[i].z);
         jia(a[i].x,a[i].y,a[i].z);
       }
     S=;
     T=n;
     for(;bfs();)
       ans+=dinic(S,inf);
     printf("%d\n",(int)ans);
     l=;
     r=;
     for(;r-l>eps;)
       {
         double mid=(l+r)/;
         jian(mid);
         ans1=;
         for(;bfs();)
           ans1+=dinic(S,inf);
         if(ans1==ans)
           {
             ss=mid;
             r=mid;
           }
         else
           l=mid;
       }
     printf("%.4lf",ss*p);
     return ;
 }

贪心 BOB肯定全加在最大权值的边上，二分权值网络流。