POJ-2031 Building a Space Station 最小生成树
题目链接：http://poj.org/problem?id=2031
很典型的最小生成树题目。
1 //STATUS:C++_AC_0MS_252KB 2 #include<stdio.h> 3 #include<stdlib.h> 4 #include<string.h> 5 #include<math.h> 6 #include<iostream> 7 #include<string> 8 #include<algorithm> 9 #include<vector> 10 #include<queue> 11 #include<stack> 12 using namespace std; 13 #define LL __int64 14 #define pii pair<int,int> 15 #define Max(a,b) ((a)>(b)?(a):(b)) 16 #define Min(a,b) ((a)<(b)?(a):(b)) 17 #define mem(a,b) memset(a,b,sizeof(a)) 18 #define lson l,mid,rt<<1 19 #define rson mid+1,r,rt<<1|1 20 const int N=110,M=1000000,INF=0x3f3f3f3f,MOD=1999997; 21 const LL LLNF=0x3f3f3f3f3f3f3f3fLL; 22 const double DNF=100000000; 23 24 struct Node{ 25 double x,y,z,r; 26 }nod[N]; 27 double w[N][N],d[N]; 28 int vis[N]; 29 int n; 30 31 inline double dist(Node &a,Node &b) 32 { 33 return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y) 34 +(a.z-b.z)*(a.z-b.z)); 35 } 36 37 double mintree() 38 { 39 int i,j,x; 40 double m,ans=0; 41 for(i=0;i<n;i++)d[i]=DNF; 42 d[0]=0; 43 mem(vis,0); 44 for(i=0;i<n;i++){ 45 m=DNF; 46 for(j=0;j<n;j++)if(d[j]<m && !vis[j])m=d[x=j]; 47 vis[x]=1; 48 ans+=d[x]; 49 for(j=0;j<n;j++){ 50 if(w[x][j]<d[j] && !vis[j]) 51 d[j]=w[x][j]; 52 } 53 } 54 return ans; 55 } 56 57 int main() 58 { 59 // freopen("in.txt","r",stdin); 60 int i,j; 61 double t; 62 while(~scanf("%d",&n) && n) 63 { 64 for(i=0;i<n;i++) 65 for(j=0;j<n;j++)w[i][j]=DNF; 66 for(i=0;i<n;i++) 67 scanf("%lf%lf%lf%lf",&nod[i].x,&nod[i].y,&nod[i].z,&nod[i].r); 68 for(i=0;i<n;i++){ 69 for(j=i;j<n;j++){ 70 t=dist(nod[i],nod[j])-nod[i].r-nod[j].r; 71 w[i][j]=w[j][i]=t>0?t:0; 72 } 73 } 74 75 printf("%.3lf\n",mintree()); 76 } 77 return 0; 78 }
