#include "stdio.h"
#include "math.h"
#define pi 3.1415926535897932384626433832795028841971
int d,n,c,g;
int k,cs[1001];
double average;
void sort()
{int i,j,temp;
 for(i=1;i<c;i++)
  for(j=1;j<c-i+1;j++)
  if(cs[j]>cs[j+1])
  {temp=cs[j];
   cs[j]=cs[j+1];
   cs[j+1]=temp;
  }
}     
double max(double a,double b)
{if(a>b) return a;
 else return b;
} 

double sin1(int i,int j)
{  if(j==1)
    return sin(average*(n-cs[i])*pi/180);
   else
   return sin(average*(cs[j]-cs[i])*pi/180);
}
double comarea()
{int i,j,t;
 int sign1,sign2;
 int mid;
 double area1,area2,aread;
 aread=0;
 for(t=3;t<=c-1;t++)
 {mid=(cs[1]+cs[t])/2;
  for(i=2;i<t&&cs[i]<mid;i++);
  if(i>=t) 
   area1=sin1(1,i-1)+sin1(i-1,t);
  else 
   area1=max(sin1(1,i)+sin1(i,t),sin1(1,i-1)+sin1(i-1,t));
  mid=(cs[t]+n)/2;
  for(j=t+1;j<c+1&&cs[j]<mid;j++);
  if(j>=c+1)
   area2=sin1(t,j-1)+sin1(j-1,1);
  else
   area2=max(sin1(t,j)+sin1(j,1),sin1(t,j-1)+sin1(j-1,1));
  if(area1+area2>aread) 
    aread=area1+area2;
 }
return (0.125*d*d*aread);
}     


int main()
{int scenario;
 int i,j,count=0;
 double area;
 scanf("%d",&scenario);
 while(scenario--)
 {scanf("%d%d%d%d",&d,&n,&c,&g);
  for(i=1,k=0;k<c;i++,k++)
  cs[i]=(g*k)%n;
  sort();
  average=360*1.0/n;
  area=comarea();
  printf("Scenario #%d:\n",++count);
  printf("%.6lf\n\n",area);
 }
return 0;
}   

• cs[i]=(g*k)%n;-->cs[i]=((__int64)g*k)%n; (0) c0500448129 2005-07-26 15:09:52
• 这个pi真精确啊 (1543) frkstyc 2005-07-26 15:18:56