luogu_1433 吃奶酪

#include<bits/stdc++.h>

using namespace std;

struct point{double x,y;}a[20];

int n;

double all=1<<30

; bool use[20];

void ( double x,double y,int sum,double ans){

if(sum==n){all=min(all,ans); return;}

for(int i=1;i<=n;i++)if(!use[i]){

double l=sqrt((x-a[i].x)*(x-a[i].x)+(y-a[i].y)*(y-a[i].y));

if(l+ans>all)continue;

use[i]=true; dfs(a[i].x,a[i].y,sum+1,ans+l); use[i]=false;

}

}

int main(){

scanf("%d",&n);

for(int i=1;i<=n;i++)scanf("%lf%lf",&a[i].x,&a[i].y);

dfs(0,0,0,0);

printf("%.2f",all);

return0;

}