137.正六边形螺旋图案

#include <graphics.h>
#include <math.h>
void polygonc();
void main()
{
  int i,r,n,x=320,y=240;
  int gdriver=9,gmode=2;
  float theta,alfa;
  n=30;
  theta=6.0;
  initgraph(&gdriver,&gmode,"c:\\tc");
  cleardevice();
  setbkcolor(MAGENTA);
  setcolor(WHITE);
  r=160;
  alfa=60.0;
  for(i=0;i<n;i++)
  {
    polygonc(x,y,r,6,alfa);
    r=(int)(0.866*r/cos((30.0-theta)*0.0174533));
    alfa=alfa+theta;
  }
  getch();
  closegraph();
}
void polygonc(x0,y0,r,n,af)
int x0,y0,n,r;
float af;
{
  int x,y,xs,ys,i;
  float dtheta,theta;
  if(n<3)
    return;
  dtheta=6.28318/n;
  theta=af*0.0174533;
  xs=x0+r*cos(theta);
  ys=y0+r*sin(theta);
  moveto(xs,ys);
  for(i=1;i<n;i++)
  {
    theta=theta+dtheta;
    x=x0+r*cos(theta);
    y=y0+r*sin(theta);
    lineto(x,y);
  }
  lineto(xs,ys);
}