> 渣渣自己写的代码：
> #include<stdio.h>
> #include<string.h>
> #include<vector>
> #include<algorithm>
> #include<queue>
> #include<cmath>
> #include<iostream>
> 
> using namespace std;
> 
> const int maxn=1005;
> vector<pair<int,double> >E[maxn];
> double x[maxn],y[maxn];
> double d[maxn];
> double maps[maxn][maxn];
> 
> void init()
> {
>     for(int i=0;i<maxn;i++)E[i].clear();
>     for(int i=0;i<maxn;i++)d[i]=1e9;
>         //for(int j=0;j<maxn;j++)
>             //d[i][j]=1e9;
> }
> 
> int main()
> {
>     int t;
>     while(~scanf("%d",&t))
>     {
>         init();
>         for(int i=1;i<=t;i++)
>         {
>             scanf("%lf%lf",&x[i],&y[i]);
>         }
> 
>         for(int i=1;i<=t;i++)
>         {
>             for(int j=1;j<=t;j++)
>             {
>                 //if(i==j)continue;
>                 maps[i][j]=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
>                 E[i].push_back(make_pair(j,maps[i][j]));
>                 E[j].push_back(make_pair(i,maps[i][j]));
>             }
>         }
>         /*for(int i=1;i<=3;i++)
>         {
>             for(int j=0;j<=5;j++)
>             {
>                 cout<<E[i][j].second<<" ";
>             }
>             cout<<endl;
>         }*/
>         //printf("%.3lf",E[1][3].second);
>         priority_queue<pair<double,int> >Q;
>         Q.push(make_pair(-d[1],1));
>         d[1]=0;
>         while(!Q.empty())
>         {
>             int now=Q.top().second;
>             Q.pop();
>             for(int i=0;i<E[now].size();i++)
>             {
>                 int v=E[now][i].first;
>                 if(d[v]>d[now]&&d[v]>E[now][i].second)
>                 {
>                     if(d[now]>E[now][i].second)
>                     {
>                         d[v]=d[now];
>                     }
>                     else if(d[now]<E[now][i].second)
>                     {
>                         d[v]=E[now][i].second;
>                     }
>                     Q.push(make_pair(-d[v],v));
>                 }
>             }
>         }
>         printf("%.3lf \n",d[2]);
> 
>     }
> }