度限制最小生成树
就是01分数规划,裸的。
#include<bits/stdc++.h>
using namespace std;
#define orz cout<<"lytcltcltcltcltcltcl"<<endl
inline int r(){int s=0,k=1;char c=getchar();while(!isdigit(c)){if(c=='-')k=-1;c=getchar();}while(isdigit(c)){s=s*10+c-'0';c=getchar();}return s*k;}
int n,m,fa[1000001];
double s;
struct node
{
int from,to;
double dis,time;
}a[1000001];
double k;
bool cmp(node x,node y)
{
return x.dis+k*x.time<y.dis+k*y.time;
}
int father(int x)
{
if(fa[x]!=x)fa[x]=father(fa[x]);
return fa[x];
}
bool check(double mid)
{
k=mid;
double sum=0;
sort(a+1,a+m+1,cmp);
for(int i=1;i<=n;i++)fa[i]=i;
for(int i=1;i<=m;i++)
{
int x=a[i].from,y=a[i].to;
int fax=father(x),fay=father(y);
if(fax==fay)continue;
fa[fax]=fay;
sum+=a[i].dis+k*a[i].time;
}
// cout<<"ahh"<<sum<<" "<<s<<endl;
if(sum<=s)
{
// cout<<"I'm ok\n";
return 1;
}
return 0;
}
int main()
{
n=r();m=r();s=r();
for(int i=1;i<=m;i++)
{
a[i].from=r();
a[i].to=r();
a[i].dis=r();
a[i].time=r();
}
double l=0,r=2e9,ans=0;
while(r-l>1e-6)
{
double mid=(l+r)/2;
if(check(mid))l=mid,ans=mid;
else r=mid;
}
printf("%.4lf",ans);
}