正解用状态压缩dp

dfs代码:
#include<bits/stdc++.h>
int n;
double mx = 0x3f3f3f3f;
int clk;
int st[20];
using namespace std;
struct zb
{
    double x, y;
}zb[20];

void dfs(double x, double y, double sum, int cnt)
{
    if(sum >= mx)
    {
        clk++;
        return;//最优性剪枝
    }
    if(cnt >= n)//可行性剪枝
    {
        mx = min(mx, sum);
//      cout << mx << endl;
        clk = 0;
        return;
    }

    for(int i = 1;i <= n;i++)
    {
        if(clk >= 35000000)return;
        if(st[i])continue;
        double xx = zb[i].x, yy = zb[i].y;
        double distance = sqrt((xx - x) * (xx - x) + (yy - y) * (yy - y));
//      if(distance >= mx)return;
        st[i] = true;
        dfs(xx, yy, sum + distance, cnt + 1);
        st[i] = false;
    }
}

int main()
{
//  ios::sync_with_stdio(0);
//  cin.tie(0);
//  cout.tie(0);
//cout << sqrt(0);
//return 0;

    cin >> n;
    for(int i = 1;i <= n;i++)cin >> zb[i].x >> zb[i].y;
    dfs(0, 0, (double)0, 0);
    printf("%.2f", mx);
    return 0;
}