poj2031

简单题

View Code

   
     

    
      #include 
    
      <
    
      iostream
    
      >
    
      
#include 
    
      <
    
      cstdio
    
      >
    
      
#include 
    
      <
    
      cstdlib
    
      >
    
      
#include 
    
      <
    
      cstring
    
      >
    
      
#include 
    
      <
    
      cmath
    
      >
    
      

    
      using
    
       
    
      namespace
    
       std;


    
      #define
    
       maxn 105
    
      

    
      #define
    
       eps 10E-9
    
      

    
      #define
    
       inf 10000000
    
      


    
      struct
    
       Point
{
 
    
      double
    
       x, y, z, r;
} point[maxn];


    
      double
    
       g[maxn][maxn];

    
      int
    
       vis[maxn], n;

    
      double
    
       lowc[maxn];


    
      double
    
       dis(Point 
    
      &
    
      a, Point 
    
      &
    
      b)
{
 Point c;
 c.x 
    
      =
    
       abs(a.x 
    
      -
    
       b.x);
 c.y 
    
      =
    
       abs(a.y 
    
      -
    
       b.y);
 c.z 
    
      =
    
       abs(a.z 
    
      -
    
       b.z);
 
    
      double
    
       ret 
    
      =
    
       sqrt(c.x 
    
      *
    
       c.x 
    
      +
    
       c.y 
    
      *
    
       c.y 
    
      +
    
       c.z 
    
      *
    
       c.z);
 
    
      if
    
       (ret 
    
      >
    
       a.r 
    
      +
    
       b.r 
    
      +
    
       eps)
 
    
      return
    
       ret 
    
      -
    
       a.r 
    
      -
    
       b.r;
 
    
      return
    
       
    
      0
    
      ;
}


    
      void
    
       input()
{
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 scanf(
    
      "
    
      %lf%lf%lf%lf
    
      "
    
      , 
    
      &
    
      point[i].x, 
    
      &
    
      point[i].y, 
    
      &
    
      point[i].z,
 
    
      &
    
      point[i].r);
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 
    
      for
    
       (
    
      int
    
       j 
    
      =
    
       
    
      0
    
      ; j 
    
      <
    
       n; j
    
      ++
    
      )
 g[i][j] 
    
      =
    
       dis(point[i], point[j]);
}


    
      double
    
       prim(
    
      double
    
       cost[][maxn], 
    
      int
    
       n)
{
 
    
      int
    
       i, j, p;
 
    
      double
    
       minc, res 
    
      =
    
       
    
      0
    
      ;
 memset(vis, 
    
      0
    
      , 
    
      sizeof
    
      (vis));
 vis[
    
      0
    
      ] 
    
      =
    
       
    
      1
    
      ;
 
    
      for
    
       (i 
    
      =
    
       
    
      1
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 lowc[i] 
    
      =
    
       cost[
    
      0
    
      ][i];
 
    
      for
    
       (i 
    
      =
    
       
    
      1
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 {
 minc 
    
      =
    
       inf;
 p 
    
      =
    
       
    
      -
    
      1
    
      ;
 
    
      for
    
       (j 
    
      =
    
       
    
      0
    
      ; j 
    
      <
    
       n; j
    
      ++
    
      )
 
    
      if
    
       (
    
      0
    
       
    
      ==
    
       vis[j] 
    
      &&
    
       minc 
    
      >
    
       lowc[j])
 {
 minc 
    
      =
    
       lowc[j];
 p 
    
      =
    
       j;
 }
 
    
      if
    
       (inf 
    
      ==
    
       minc)
 
    
      return
    
       
    
      -
    
      1
    
      ;
 res 
    
      +=
    
       minc;
 vis[p] 
    
      =
    
       
    
      1
    
      ;
 
    
      for
    
       (j 
    
      =
    
       
    
      0
    
      ; j 
    
      <
    
       n; j
    
      ++
    
      )
 
    
      if
    
       (
    
      0
    
       
    
      ==
    
       vis[j] 
    
      &&
    
       lowc[j] 
    
      >
    
       cost[p][j])
 lowc[j] 
    
      =
    
       cost[p][j];
 }
 
    
      return
    
       res;
}


    
      int
    
       main()
{
 
    
      //
    
      freopen("t.txt", "r", stdin);
    
      

    
       
    
      while
    
       (scanf(
    
      "
    
      %d
    
      "
    
      , 
    
      &
    
      n), n)
 {
 input();
 
    
      double
    
       ans 
    
      =
    
       prim(g, n);
 printf(
    
      "
    
      %.3f\n
    
      "
    
      , ans);
 }
 
    
      return
    
       
    
      0
    
      ;
}