Steiner tree

Gym - 101908J Joining Capitals

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 105;
const double INF = 1e12;
pair<int, int> p[MAXN];
double dp[MAXN][1 << 11], 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 = 0; i < n; i++) {
                scanf("%d %d", &p[i].first, &p[i].second);
        }
        for (int i = 0; i < n; i++) {
                for (int j = 0; 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 = 0; j < (1 << k); j++) {
                        dp[i][j] = 0;
                        for (int s = 0; s < k; s++) {
                                dp[i][j] += (j >> s & 1) * dis[i][s];
                        }
                }
        }
        for (int S = 0; S < (1 << 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 - 1)&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][(1 << k) - 1]);
        }
        printf("%.5f
", ans);
        return 0;
}