POJ2031 Building a Space Station 最小生成树 知道么 c++ 双精度 用%lf G++用 %f 我勒个去 不然会wa啊！！！

自己的方法#include<stdio.h>#include<string.h>#include<math.h>#include<algorithm>using namespace std;struct Island{    double xi,yi,zi,r;    int father;}island[101];double dist(Island A,Island B)  {      return sqrt((A.xi-B.xi)*1.0*(A.xi-B.xi)+(A.yi-B.yi)*(A.yi-B.yi)+(A.zi-B.zi)*(A.zi-B.zi))-A.r-B.r;  }  struct Bridge{    int a,b;    double price;}bridge[10010];int cmp(Bridge a,Bridge b){    return a.price < b.price;}int find(int x){    int t;    int child = x;    while(x != island[x].father)    {        x = island[x].father;    }        while(x != child)        {            t=island[child].father;            island[child].father = x;            child = t;        }       return x;}int merge(int x,int y){    int a =find(x);    int b =find(y);    if(a != b)    {        island[a].father = b;        return 1;    }    return 0;   } int main(){    int n,m,i,j,k,g,t; //g 是用来优化最后一步  如果当所有的岛都联通之后 停止 造桥     double ans;    while(scanf("%d",&n),n)     {        k = 1;        g =1;        ans = 0.000;        memset(bridge,0,sizeof(bridge));        memset(island,0,sizeof(island));        for(i = 0;i <= 100;i++ )        island[i].father = i;        for (i = 1;i <= n;i++)        {            scanf("%lf%lf%lf%lf",&island[i].xi,&island[i].yi,&island[i].zi,&island[i].r);            for( j = 1;j < i;j++)            {                if(dist(island[i],island[j]) > 0)                               {                bridge[k].a = i;                bridge[k].price = dist(island[i],island[j]);                bridge[k++].b = j;                 }                else                {                bridge[k].a = i;                bridge[k].price = 0.000;                bridge[k++].b = j;                 }            }               }               sort(bridge+1,bridge+k,cmp);            for(i = 1;i < k;i++)            {                if (merge(bridge[i].a,bridge[i].b))                {                ans += bridge[i].price;                g++;                }                               if(g == n)                break;            }            printf("%.3lf\n",ans);    }    return 0;}网上的方法1这个真的是太简洁 了    好飘逸  ！！！  prim 算法  好好学！！！#include<cstdio>  #include<iostream>  #include<cmath>  using namespace std;  const int mm=111;  double x[mm],y[mm],z[mm],r[mm],dis[mm];  bool p[mm];  int i,j,k,n;  double mn,ans;  double sq(double a)  {      return a*a;  }  double dd(int i,int j)  {      double ret=sqrt(sq(x[i]-x[j])+sq(y[i]-y[j])+sq(z[i]-z[j]))-r[i]-r[j];      return ret>0?ret:0;  }  int main()  {      while(scanf("%d",&n),n)      {          for(i=1;i<=n;++i)              scanf("%lf%lf%lf%lf",&x[i],&y[i],&z[i],&r[i]);          for(i=1;i<=n;++i)dis[i]=1e30,p[i]=1;          ans=dis[1]=0;          for(i=1;i<=n;++i)          {              mn=1e30;              for(j=1;j<=n;++j)                  if(p[j]&&dis[j]<mn)                  {                      mn=dis[j];                      k=j;                  }              p[k]=0;              ans+=mn;              for(j=1;j<=n;++j)                  if(p[j])dis[j]=min(dis[j],dd(k,j));          }          printf("%.3lf\n",ans);      }      return 0;  } 网上的方法2 #include<stdio.h>#include<math.h>#include<string.h>#define N 99999999struct node {   double x,y,z,r;}lnode[150];double map[150][150];double d[150];int flag[150],n;double dist(int a,int b){   double sum;   sum=sqrt(pow((lnode[a].x-lnode[b].x),2)+pow((lnode[a].y-lnode[b].y),2)+pow((lnode[a].z-lnode[b].z),2))-lnode[a].r-lnode[b].r;   return sum;}double prim(){   int i,j,z;   double min,sum=0;   memset(flag,0,sizeof(flag));   for(i=0;i<n;i++)       d[i]=map[0][i];   flag[0]=1;   for(i=1;i<n;i++)   {       min=N;       for(j=1;j<n;j++)           if(!flag[j]&&d[j]<min)           {               min=d[j];               z=j;           }           flag[z]=1;           //printf("%.3f\n",min);           sum+=min;           for(j=0;j<n;j++)               if(!flag[j]&&d[j]>map[j][z])                   d[j]=map[z][j];   }   return sum;}int main(){   int i,j;   while(scanf("%d",&n),n)   {       for(i=0;i<n;i++)           scanf("%lf%lf%lf%lf",&lnode[i].x,&lnode[i].y,&lnode[i].z,&lnode[i].r);       for(i=0;i<n;i++)           for(j=0;j<n;j++)               map[i][j]=N;       for(i=0;i<n;i++)           for(j=i+1;j<n;j++)           {               double v=dist(i,j);               //printf("%.3f\n",v);               if(v<=0)               {                   map[i][j]=0;                   map[j][i]=0;               }               else               {                   map[i][j]=v;                   map[j][i]=v;               }           }           printf("%.3f\n",prim());   }   return 0;}