URAL1084[Goat in the Garden]

水题，分三种情况讨论就行了。

CODE:

/*

PROGRAM: $PROGRAM

AUTHOR: Su Jiao

DATE: 2010-4-11

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::M_PI;

#define M_PI 3.141592653589793238462643383279f

using std::sqrt;

 

class Application

{

      double A,R;

      public:

      Application()

      {

                   cin>>A>>R;

      }

      int run()

      {

          cout<<std::setiosflags(std::ios::fixed)<<std::setprecision(3);

          if (R*2<=A)

             cout<<M_PI*R*R<<endl;

          else if (R*sqrt(2.0)>=A) cout<<A*A<<endl;

          else

          {

              double a=A/2;

              double c=R;

              double b=sqrt(c*c-a*a);

              cout<<(b*a+M_PI*R*R*((M_PI/2)-acos(a/c)*2)/(M_PI*2))*4<<endl;

          }

          return 0;

      }

};

 

int main()

{

    Application app;

    return app.run();

}