HDU 3405 World Islands

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 using namespace std;
 6 const int maxn = 55;
 7 const int INF = 0x3f3f3f3f;
 8 struct Point {
 9     int x,y;
10 } p[maxn];
11 double dis[maxn][maxn],tmp[maxn][maxn],d[maxn];
12 bool done[maxn];
13 int n;
14 double prim(){
15     double ans = 0;
16     for(int i = 0; i < n; ++i){
17         done[i] = false;
18         d[i] = INF;
19     }
20     d[0] = 0;
21     for(int k = 0; k < n; ++k){
22         double minV = INF;
23         int idx = 0;
24         for(int i = 0; i < n; ++i)
25             if(!done[i] && minV > d[i]) minV = d[idx = i];
26         ans += d[idx];
27         done[idx] = true;
28         for(int i = 0; i < n; ++i)
29             if(!done[i] && d[i] > dis[idx][i])
30                 d[i] = dis[idx][i];
31     }
32     return ans;
33 }
34 double getDis(int i,int j){
35     double tmp = (p[i].x - p[j].x)*(p[i].x - p[j].x);
36     tmp += (p[i].y - p[j].y)*(p[i].y - p[j].y);
37     return sqrt(tmp);
38 }
39 int main(){
40     int T;
41     scanf("%d",&T);
42     while(T--){
43         scanf("%d",&n);
44         for(int i = 0; i < n; ++i){
45             scanf("%d %d",&p[i].x,&p[i].y);
46             for(int j = i - 1; j >= 0; --j){
47                 tmp[i][j] = tmp[j][i] = getDis(i,j);
48             }
49         }
50         double ans = INF;
51         for(int i = 0; i < n; ++i){
52             memcpy(dis,tmp,sizeof(tmp));
53             for(int j = 0; j < n; ++j)
54                 dis[i][j] = dis[j][i] = INF>>1;
55             ans = min(ans,prim());
56         }
57         printf("%.2f\n",ans-(INF>>1));
58     }
59     return 0;
60 }