输入的 (1 \leq k \leq n \leq 100)，(1 \leq a[i] \leq n) 且所有的 (a[i]) 不会重复，((x[i], y[i])) 代表点的坐标，坐标在 0 到 100 之间，且为整数（但是用 double 存储），所有的坐标互不重复。
cpp
1#include <bits/stdc++.h>
2using namespace std;
3const double eps = 1e-5;
4double x[105], y[105], cx[105], cy[105];
5int n, k, a[105], id[105];
6vector<int> v[105];
7,[object Object],
8,[object Object],
9,[object Object],
10,[object Object],
11,[object Object],
cpp
1int main(){,[object Object],
2cin >> n >> k;,[object Object],
3for (int i = 1; i <= n; i++){,[object Object],
4cin >> x[i] >> y[i];,[object Object],
5id[i] = i; // 第43行,[object Object],
6},[object Object],
7for (int i = 1; i <= k; i++){,[object Object],
8cin >> a[i];,[object Object],
9cx[i] = x[a[i]]; cy[i] = y[a[i]];,[object Object],
10},[object Object],
11while (solve());,[object Object],
12printf("%.2lf", cal());,[object Object],
13return 0;,[object Object],
14},[object Object],