POJ-2031 Building a Space Station---MST + 空间距离

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<cmath>
 6 #include<queue>
 7 #include<stack>
 8 #include<map>
 9 #include<sstream>
10 using namespace std;
11 typedef long long ll;
12 const int maxn = 2e2 + 10;
13 const int INF = 1 << 30;
14 int dir[4][2] = {1,0,0,1,-1,0,0,-1};
15 int T, n, m, x;
16 struct node
17 {
18     double x, y, z, r;
19     node(){}
20     node(double x, double y, double z, double r):x(x), y(y), z(z), r(r){}
21 };
22 node a[maxn];
23 double Map[maxn][maxn];//存图
24 double lowcost[maxn], mst[maxn];
25 void prim(int u)//最小生成树起点
26 {
27     double sum_mst = 0;//最小生成树权值
28     for(int i = 1; i <= n; i++)//初始化两个数组
29     {
30         lowcost[i] = Map[u][i];
31         mst[i] = u;
32     }
33     mst[u] = -1;//设置成-1表示已经加入mst
34     for(int i = 1; i <= n; i++)
35     {
36         double minn = INF;
37         int v = -1;
38         //在lowcost数组中寻找未加入mst的最小值
39         for(int j = 1; j <= n; j++)
40         {
41             if(mst[j] != -1 && lowcost[j] < minn)
42             {
43                 v = j;
44                 minn = lowcost[j];
45             }
46         }
47         if(v != -1)//v=-1表示未找到最小的边,
48         {//v表示当前距离mst最短的点
49             //printf("%d %d %d\n", mst[v], v, lowcost[v]);//输出路径
50             mst[v] = -1;
51             sum_mst += lowcost[v];
52             for(int j = 1; j <= n; j++)//更新最短边
53             {
54                 if(mst[j] != -1 && lowcost[j] > Map[v][j])
55                 {
56                     lowcost[j] = Map[v][j];
57                     mst[j] = v;
58                 }
59             }
60         }
61     }
62     //printf("weight of mst is %d\n", sum_mst);
63     printf("%.3f\n", sum_mst);
64 }
65 double f(int i, int j)
66 {
67     double l;
68     l = sqrt((a[i].x - a[j].x) * (a[i].x - a[j].x) + (a[i].y - a[j].y) * (a[i].y - a[j].y) + (a[i].z - a[j].z) * (a[i].z - a[j].z));
69     l = l - a[i].r - a[j].r;
70     if(l <= 0)return 0;
71     else return l;
72 }
73 int main()
74 {
75     while(cin >> n && n)
76     {
77         for(int i = 1; i <= n; i++)cin >> a[i].x >> a[i].y >> a[i].z >> a[i].r;
78         for(int i = 1; i <= n; i++)
79         {
80             for(int j = i; j <= n; j++)
81             {
82                 Map[i][j] = Map[j][i] = f(i, j);
83             }
84         }
85         prim(1);
86     }
87     return 0;
88 }