n^3暴力过了
#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
struct point{
double x,y;
}p[1001];
inline double dis(point a,point b)
{
return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
int main()
{
int t,n,cas=1;
scanf("%d",&t);
while(t--)
{
double ans=0x3f3f3f3f;
scanf("%d",&n);
for(int i=0;i<n;i++) scanf("%lf%lf",&p[i].x,&p[i].y);//cin>>p[i].x>>p[i].y;
for(int i=0;i<n;i++)
{
for(int j=i+1;j<n;j++)
{
double tmp=dis(p[i],p[j]),tmp2;
if(tmp*2>=ans) continue;
for(int k=j+1;k<n;k++)
{
if((p[j].y-p[i].y)*(p[k].x-p[i].x)==(p[k].y-p[i].y)*(p[j].x-p[i].x)) continue;
tmp2=tmp+dis(p[i],p[k])+dis(p[j], p[k]);
if(tmp2<ans) ans=tmp2;
}
}
}
printf("Case %d: ",cas++);
if(ans<0x2f2f2f2f) printf("%.3lf\n",ans);
else printf("No Solution\n");
}
}