100分hack有两个不过求调玄关

#include<bits/stdc++.h>
using namespace std;
const int N=20,M=10000000;
int n,cnt;
double x[N]={0},y[N]={0},dist[N][N],ans=1e6;
bool vis[N];
void dfs(int dth,int now,double sum)
{
	cnt++;
	if(cnt>=M)
	{
		cout<<fixed<<setprecision(2)<<ans<<'\n';
		exit(0);
	}
	if(dth>n)
	{
		if(sum<ans) ans=sum;
		return ;
	}
	for(int i=1;i<=n;i++)
	{
		if(!vis[i])
		{
			double t=sum+dist[now][i];
			if(t>=ans) continue;
			vis[i]=1;
			dfs(dth+1,i,t);
			vis[i]=0;
		}
	}
}
signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>x[i]>>y[i];
	}
	for(int i=0;i<=n;i++)
	{
		for(int j=0;j<=n;j++)
		{
			dist[i][j]=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
		}
	}
	dfs(1,0,0);
	cout<<fixed<<setprecision(2)<<ans<<'\n'; 
	
	
	return 0;
}