URAL1075[A thread in a space]

数学题。

CODE:

/*

PROGRAM: $PROGRAM

AUTHOR: Su Jiao

DATE: 2010-4-9

DESCRIPTION:

$DESCRIPTION

*/

#include <iostream>

using std::cin;

using std::cout;

#include <fstream>

using std::ifstream;

using std::ofstream;

#include <sstream>

using std::stringstream;

using std::endl;

#include <vector>

using std::vector;

#include <string>

using std::string;

#include <stack>

using std::stack;

#include <queue>

using std::queue;

using std::priority_queue;

#include <set>

using std::set;

#include <map>

using std::map;

using std::pair;

using std::make_pair;

#include <algorithm>

using std::sort;

#include <iomanip>

#include <cassert>

//using std::assert;

#include <cmath>

using std::sqrt;

using std::acos;

 

struct Point{double x,y,z;};

double d(const Point& A,const Point& B)

{

       return sqrt((A.x-B.x)*(A.x-B.x)

                  +(A.y-B.y)*(A.y-B.y)

                  +(A.z-B.z)*(A.z-B.z));

}

double s(double a,double b,double c)

{

       double p=(a+b+c)/2;

       return sqrt(p*(p-a)*(p-b)*(p-c));

}

 

class Application

{

      Point A,B,C;

      double R;

      public:

      Application()

      {

                   cin>>A.x>>A.y>>A.z

                      >>B.x>>B.y>>B.z

                      >>C.x>>C.y>>C.z

                      >>R;

      }

      int run()

      {

          double AB=d(A,B);

          double AC=d(A,C);

          double BC=d(B,C);

         

          cout<<std::setiosflags(std::ios::fixed)<<std::setprecision(2);

          if (acos((AC*AC+BC*BC-AB*AB)/(2*AC*BC))-acos(R/AC)-acos(R/BC)<0)

             cout<<AB<<endl;

          else

          {

              double answer=0;

              answer=

              sqrt(AC*AC-R*R)

              +sqrt(BC*BC-R*R)

              +R*(acos((AC*AC+BC*BC-AB*AB)/(2*AC*BC))-acos(R/AC)-acos(R/BC));

              cout<<answer<<endl;

          }

          return 0;

      }

};

 

int main()

{

    Application app;

    return app.run();

}