#include <iostream.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <conio.h>
#include <graphics.h>
typedef  struct {
int x,y,pred,succ;
}punct;
typedef punct poligon[10];
poligon p;
int n,i;
int orientare(punct A, punct B, punct C)
{
float d;
d=(float)(B.x-A.x)*(C.y-A.y)-(C.x-A.x)*(B.y-A.y);
if(d>0)return 1;
if(d<0)return -1;
if(d==0)return 0;
}
int coliniare(punct A,punct B, punct C)
{
	if(orientare(A,B,C)!=0) return 0;
	else return 1;
}
void citire_poligon()
{
printf("n=");
scanf("%d",&n);
for(i=0;i<n;i++)
{
printf("Dati p[%d].x=",i);
scanf("%d",&p[i].x);
printf("Dati p[%d].y=",i);
scanf("%d",&p[i].y);
p[i].pred=(n+i-1)%n;
p[i].succ=(i+1)%n;
}
}
void desenare_poligon(int n,poligon p)
{
char c[3];
moveto(p[n-1].x,p[n-1].y);
for(i=0;i<n;i++)
{
lineto(p[i].x,p[i].y);
itoa(i,c,10);
outtextxy(p[i].x,p[i].y,c);
}
}
int intre(punct A, punct B,punct C)
{
	if(!coliniare(A,B,C)) return 0;
	if(A.x<C.x) return (((A.x<B.x)&&(B.x<=C.x))||((A.x>=B.x)&&(B.x>=C.x)));
	else
	return (((A.y<=B.y)&&(B.y<=C.y))||((A.y>=B.y)&&(B.y>=C.y)));
}
int intersectie_proprie(punct A,punct B,punct C,punct D)
{
return((orientare(A,B,C)*orientare(A,B,D)<0)&&(orientare(C,D,A)*orientare(C,D,B)<0));
}
int intersectie_improprie(punct A,punct B,punct C,punct D)
{
if(intre(C,A,D)||intre(C,B,D)||intre(A,C,D)||intre(A,D,B)) return 1;
else return 0;
}

int intersectie_segmente(punct A,punct B,punct C,punct D)
{
if(intersectie_proprie(A,B,C,D)||intersectie_improprie(A,B,C,D)) return 1;
else return 0;
}
int poligon_simplu(int n, poligon p){
int i,k;
for(i=0;i<n;i++)
for(k=0;k<n;k++)
if((i!=k)&&(i!=(k+1)%n)&&(k!=(i+1)%n)&& intersectie_segmente(p[i],p[(i+1)%n],p[k],p[(k+1)%n])) return 0;
return 1;
}
int orientare_poligon(int n,poligon p)
{
int m=0;
for(int i=1;i<n;i++)
if((p[m].y>p[i].y)||((p[m].y==p[i].y)&&(p[m].x<p[i].x)))m=i;
return orientare(p[(m-1+n)%n],p[m],p[(m+1)%n]);
}
void main()
{
clrscr();
int gd=DETECT,gm;
initgraph(&gd,&gm,"C:\\bc31\\bgi");
cleardevice();
setbkcolor(BLUE);
citire_poligon();
cleardevice();
desenare_poligon(n,p);
getch();
cleardevice();
printf("Poligon simplu %d\n",poligon_simplu(n,p));
getch();
cleardevice();
if(orientare_poligon(n,p)==1)
printf("Poligon orientat pozitiv");
if(orientare_poligon(n,p)==-1)
printf("Poligon orientat negativ");

getch();
closegraph();
}