水题求助

#include<iostream>
#include<cmath>
#include<algorithm>
using namespace std;
double d[210][210];
int x[30],y[30];
int n;double ans=1e9;bool vis[30];

void dfs(int last, double sum,int u)
{
	if(u>n)
	{
		ans=min(ans,sum);
		return;
	}
	for(int i = 1; i <= n; i++)
	{
		if(vis[i]==1)continue;
		vis[i]=1;
		int w=d[last][i];
		dfs(i,w+sum,u+1);
		vis[i]=0;
	}
}
int main()
{
	cin >> n;
	for(int i = 1; i <= n; i++)
	{
		cin >> x[i] >> y[i];
	}
	for(int i = 1; i <= n; i++)
	{
		for(int j = 1; j <= n; j++)
		{
			d[i][j]=sqrt((x[j]-x[i])*(x[j]-x[i])+(y[j]-y[i]*(y[j]-y[i])));
		}
	}
	dfs(0,0,1);
	
	cout << ans;
	
}