analizarConvexos.c

/*
 * @authors Equipo docente programacion grado de ingenieria
 * @university  UAL
 * @date 2019-02-06

*  */



#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <ctype.h>
#include <math.h>

int main(){
	char c;
	float e1x,e1y,ex,ey,eantx,eanty;
	float x1,y1,x,y,xant,yant;
	float z;
	int pos,neg;
	int n,i;
	do{ system("cls");
		printf("CONCAVIDAD/CONVEXIDAD POLIGONO\n");
		printf("==============================\n\n");
		do{	printf("Num. de vertices: ");
			scanf(" %d",&n);
		}while(n<3);
		i=1;
		pos=0;
		neg=0;
		printf("Coordenadas vertice %d:\n",i);
		printf("\tx: ");
		scanf(" %f",&x1);
		printf("\ty: ");
		scanf(" %f",&y1);
		i=2;
		printf("Coordenadas vertice %d:\n",i);
		printf("\tx: ");
		scanf(" %f",&xant);
		printf("\ty: ");
		scanf(" %f",&yant);
		e1x=xant-x1;
		e1y=yant-y1;
		eantx=e1x;
		eanty=e1y;
        i=3;
		while(i<=n){
			printf("Coordenadas vertice %d:\n",i);
			printf("\tx: ");
			scanf(" %f",&x);
			printf("\ty: ");
			scanf(" %f",&y);
			ex=x-xant;
			ey=y-yant;
			z=eantx*ey-eanty*ex;
			if(z>0){
				pos++;
			}else{
				if(z<0){
					neg++;
				}
			}
			xant=x;
			yant=y;
			eantx=ex;
			eanty=ey;
			++i;
		}
		ex=x1-xant;
		ey=y1-yant;
		z=eantx*ey-eanty*ex;
		if(z>0){
			pos++;
		}else{
			if(z<0){
				neg++;
			}
		}
		z=ex*e1y-ey*e1x;
		if(z>0){
			pos++;
		}else{
			if(z<0){
				neg++;
			}
		}
		if(pos){
			if(neg){
				printf("\nPoligono concavo");
			}else{
				printf("\nPoligono convexo");
			}
		}else{
			if(neg){
				printf("\nPoligono convexo");
			}else{
				printf("\nPoligono degenerado en una linea");
			}
		}
		printf("\n\nDesea efectuar una nueva operacion (s/n)? ");
		c=toupper(getch());
	}while (c!='N');
	return 0;
}