Steiner tree

Gym - 101908J Joining Capitals

 #include<bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 const int MAXN = ;
 const double INF = 1e12;
 pair<int, int> p[MAXN];
 double dp[MAXN][ << ], dis[MAXN][MAXN];
 int N2(int x) {
         return x * x;
 }
 double get_dis(pair<int, int> a, pair<int, int> b) {
         return sqrt(N2(a.first - b.first) + N2(a.second - b.second));
 }
 int main() {
         int n, k;
         scanf("%d %d", &n, &k);
         for (int i = ; i < n; i++) {
                 scanf("%d %d", &p[i].first, &p[i].second);
         }
         for (int i = ; i < n; i++) {
                 for (int j = ; j < n; j++) {
                         if (i != j) {
                                 dis[i][j] = get_dis(p[i], p[j]);
                         }
                 }
         }
         for (int i = k; i < n; i++) {
                 for (int j = ; j < ( << k); j++) {
                         dp[i][j] = ;
                         for (int s = ; s < k; s++) {
                                 dp[i][j] += (j >> s & ) * dis[i][s];
                         }
                 }
         }
         for (int S = ; S < ( << k); S++) {
                 for (int x = k; x < n; x++) {
                         for (int i = k; i < n; i++) {
                                 if (i != x) {
                                         for (int sub = S; ; sub = (sub - )&S) {
                                                 dp[x][S] = min(dp[x][S], dis[i][x] + dp[x][sub] + dp[i][S ^ sub]);
                                                 if (!sub) {
                                                         break;
                                                 }
                                         }
                                 }
                         }
                 }
         }
         double ans = INF;
         for (int i = k; i < n; i++) {
                 ans = min(ans, dp[i][( << k) - ]);
         }
         printf("%.5f\n", ans);
         return ;
 }