DFS 70pts求主助

#include<bits/stdc++.h>
using namespace std;
typedef pair<double,double> PII;
#define x first
#define y second
const int N=30;
int n;
double dist[N][N];
bool st[N];
double ans=1e9;
void dfs(int u,double distance){
    if(st[u]){
        ans=min(ans,distance);
        return;
    }
	st[u]=true;
	int nu=-1;
	double dis=1e9;
	for(int i=0;i<n;i++){
		if(st[i]) continue;
		if(dist[u][i]<dis){
			nu=i;
			dis=dist[u][i];
		}
	}
	if(nu==-1){
	    ans=min(ans,distance);
	    return;
	}
	dfs(nu,distance+dist[u][nu]);
}
int main()
{
	cin>>n;
	vector<PII> a(n);
	double init=1e9;
	for(int i=0;i<n;i++){
	    cin>>a[i].x>>a[i].y;
	    init=min(init,sqrt((a[i].x*a[i].x)+(a[i].y*a[i].y)));
	}
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++){
			if(i==j){
				dist[i][j]=1e9;
				continue;
			}
			dist[i][j]=
			sqrt((a[i].x-a[j].x)*(a[i].x-a[j].x)+(a[i].y-a[j].y)*(a[i].y-a[j].y));
		}
	}
	for(int i=0;i<n;i++){
	    memset(st,false,sizeof st);
	    dfs(i,0);
	}
    printf("%.2lf\n",init+ans);
	return 0;
}