1 #include<iostream>
2 #include<algorithm>
3 #include<cmath>
4 #include<iomanip>
5 #define MAXN 105
6 #define inf 1000000000
7 using namespace std;
8
9 typedef double elem_t;
10
11 double point[MAXN][2];
12 double _m[MAXN][MAXN];
13 int pre[MAXN];
14 elem_t prim(int n,elem_t mat[][MAXN],int* pre);
15 int main()
16 {
17 //freopen("acm.acm","r",stdin);
18 int num;
19 int i;
20 int j;
21 double x;
22 double y;
23 cin>>num;
24 for(i = 0; i < num; ++ i)
25 {
26 cin>>point[i][0]>>point[i][1];
27 }
28 for(i = 0; i < num; ++ i)
29 {
30 for(j = i+1; j < num; ++ j)
31 {
32 _m[i][j] = sqrt((point[i][0] - point[j][0])*(point[i][0] - point[j][0]) + (point[i][1] - point[j][1])*(point[i][1] - point[j][1]));
33 _m[j][i] = _m[i][j];
34 }
35 }
36 cout<<setiosflags(ios::fixed)<<setprecision(2)<<prim(num,_m,pre)<<endl;
37 }
38
39
40 elem_t prim(int n,elem_t mat[][MAXN],int* pre){
41 elem_t min[MAXN],ret=0;
42 int v[MAXN],i,j,k;
43 for (i=0;i<n;i++)
44 min[i]=inf,v[i]=0,pre[i]=-1;
45 for (min[j=0]=0;j<n;j++){
46 for (k=-1,i=0;i<n;i++)
47 if (!v[i]&&(k==-1||min[i]<min[k]))
48 k=i;
49 for (v[k]=1,ret+=min[k],i=0;i<n;i++)
50 if (!v[i]&&mat[k][i]<min[i])
51 min[i]=mat[pre[i]=k][i];
52 }
53 return ret;
54 }
