80分·，求解，2个WA。

#include<bits/stdc++.h>
using namespace std;
int n,v[1001];
double x[100];
double y[20];
double dis[1001][1001];
double ans=1231234424.0;
int read() {
    int ans=0,flag=1;
    char ch=getchar();
    while( (ch>'9' || ch<'0') && ch!='-' ) ch=getchar();
    if(ch=='-') flag=-1,ch=getchar();
    while(ch>='0' && ch<='9') ans=ans*10+ch-'0',ch=getchar();
    return ans*flag;
}
void dfs(int step,int now,double length)
{
    if(length>ans)
      return;                                                                                                    
    if(step==n) 
      {
          ans=min(ans,length);
          return;
      }
    for(int i=1;i<=n;i++)  
      if(!v[i])   
        {
            v[i]=1; 
            dfs(step+1,i,length+dis[now][i]);  
            v[i]=0;  
        }
}
int main()
{
    n=read();
    for(int i=1;i<=n;i++)
      x[i]=read(),y[i]=read();
    x[0]=0;y[0]=0;  
    for(int i=0;i<=n;i++) 
      for(int j=0;j<=n;j++)
        dis[i][j]=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
    dfs(0,0,0.0); 
    printf("%.2f\n",ans);
    return 0;
}