C语言编程小弟急需答案请高人帮助!!!!!!!!!!!1

#include<graphics.h>
int set(int *p,int r,int x,int y){
*(p+0)=x-r/2;
*(p+1)=y-r;
*(p+2)=x+r/2;
*(p+3)=y-r;
*(p+4)=x+r;
*(p+5)=y;
*(p+6)=x+r/2;
*(p+7)=y+r;
*(p+8)=x-r/2;
*(p+9)=y+r;
*(p+10)=x-r;
*(p+11)=y;
*(p+12)=x-r/2;
*(p+13)=y-r;

}
main()
{int gd=DETECT,gm;
int i=10;
int x=350,y=220;
int *p;
initgraph(&gd,&gm,"");
setbkcolor(9);
setcolor(14);
set(p,i,x,y);
drawpoly(7, p);
while(getch()!='\r'){
i=i+10;
cleardevice();
set(p,i,x,y);
drawpoly(7, p);
setbkcolor(9);
setcolor(14);
}
}
i为外接圆半径，x，y为圆心，按回车结束

有点难~~