/*******************************************
*	Ime i Prezime: Bojan Delic
*	Broj indexa: 11510
*	Godina studija: 1
*	Datum: 16.11.2005
*	Verzija: 0.1
********************************************/


/*******************************************
*
*  Program koji racuna obim trouga na osnovu
*  unetih koordinata u koordinatnom sistemu
*
*******************************************/
#include <stdio.h>
#include <math.h>
main () {
	/***********************************************
	*
	*  x1, x2 i x3 su koordinate na X osi za tri tacke
	*  y1, y2 i y3 su koordinate na Y osi za tri tacke
	*  a, b i c su stranice trougle
	*  O je obim trougla
	*
	************************************************/
	double x1, x2, x3, y1, y2, y3, a, b, c, O;  
	
	
	/****************************************
	*
	*  again je pomocna promenljiva koja sluzi za vracanje programa na pocetak 
	*  ako korinsik hoce da ponovi program
	*
	*****************************************/
	char again = 'y';
	
	
	/*****************************************
	*
	*  Prvo unosenje koordinata tacaka!
	*  Kasnije sledi provera da li se neke tacke poklapaju
	*
	*******************************************/
	printf("**Program za racunanje obima trougla pomocu koordinata**\n");
	while(again=='y') {
	/****************************************
	*
	*  Unos prve tacke
	*
	*****************************************/
	printf("\nUnesite koordinate prve tacke: ");
	printf("\n\tx= ");
	scanf("%lf", &x1);
	printf("\ty= ");
	scanf("%lf", &y1);
	/****************************************
	*
	*  Unos druge tacke
	*
	*****************************************/
	printf("\nUnesite koordinate druge tacke: ");
	printf("\n\tx= ");
	scanf("%lf", &x2);
	printf("\ty= ");
	scanf("%lf", &y2);
	/****************************************
	*
	*  Unos trece tacke
	*
	*****************************************/
	printf("\nUnesite koordinate trece tacke: ");
	printf("\n\tx= ");
	scanf("%lf", &x3);
	printf("\ty= ");
	scanf("%lf", &y3);
	
	/******************************************
	*
	*  Racunanje duzine stranice pomocu koordinata
	*  dve tacke u koordinatnom sistemu!
	*
	*******************************************/
	a = sqrt(pow((x1-x2), 2)+pow((y1-y2), 2));
	b = sqrt(pow((x2-x3), 2)+pow((y2-y3), 2));
	c = sqrt(pow((x1-x3), 2)+pow((y1-y3), 2));


	/*************************************************
	*
	*  Provera da li je bar jedna od stranica trugla jednaka nuli
	*  Ako jeste to znaci da se neke koordinate poklapaju
	*  U tom slucaju trazi se od korisnika da ponovo unese koordinate
	*  krajnjih tacaka stranice koja je jedanaka nuli
	*
	***************************************************/
	while (a==0 || b==0 || c==0) {
		/*********************************************************
		*
		*  Ako je stranica a jednaka nuli, prva i druga tacka se poklapaju
		*
		**********************************************************/
		while (a==0) {
			printf("\nKoorinate prve i druge tacke se poklapaju!\n");
			/****************************************
			*
			*  Unos prve tacke
			*
			*****************************************/
			printf("\nUnesite koordinate prve tacke: ");
			printf("\n\tx= ");
			scanf("%lf", &x1);
			printf("\ty= ");
			scanf("%lf", &y1);
			
			/****************************************
			*
			*  Unos druge tacke
			*
			*****************************************/
			printf("\nUnesite koordinate druge tacke: ");
			printf("\n\tx= ");
			scanf("%lf", &x2);
			printf("\ty= ");
			scanf("%lf", &y2);
			
			a = sqrt(pow((x1-x2), 2)+pow((y1-y2), 2));
		}
		/*******************************************************
		*
		*  Ako je stranica b jednaka nuli, druga i treca tacka se poklapaju
		*
		********************************************************/
		while (b==0) {
			printf("\nKoorinate druge i trece tacke se poklapaju!\n");
			/****************************************
			*
			*  Unos druge tacke
			*
			*****************************************/
			printf("\nUnesite koordinate druge tacke: ");
			printf("\n\tx= ");
			scanf("%lf", &x2);
			printf("\ty= ");
			scanf("%lf", &y2);
			
			
			/****************************************
			*
			*  Unos trece tacke
			*
			*****************************************/
			printf("\nUnesite koordinate trece tacke: ");
			printf("\n\tx= ");
			scanf("%lf", &x3);
			printf("\ty= ");
			scanf("%lf", &y3);
			
			b = sqrt(pow((x2-x3), 2)+pow((y2-y3), 2));
		}
		/******************************************************
		*
		*  Ako je stranica c jednaka nuli, prva i treca tacka se poklapaju
		*
		********************************************************/
		while (c==0) {
			printf("\nKoorinate prve i trece tacke se poklapaju!\n");
			
			/****************************************
			*
			*  Unos prve tacke
			*
			*****************************************/
			printf("\nUnesite koordinate prve tacke: ");
			printf("\n\tx= ");
			scanf("%lf", &x1);
			printf("\ty= ");
			scanf("%lf", &y1);
			
			/****************************************
			*
			*  Unos trece tacke
			*
			*****************************************/
			printf("\nUnesite koordinate trece tacke: ");
			printf("\n\tx= ");
			scanf("%lf", &x3);
			printf("\ty= ");
			scanf("%lf", &y3);
			
			c = sqrt(pow((x1-x3), 2)+pow((y1-y3), 2));
		}
		
		/*****************************************************
		*
		*  Ponovno racunanje stranica je neophodno jer
		*  moze da se desi da se na primer prva i treca koordinara 
		*  poklapaju, odnosno da je stranica c jednaka nulu. 
		*  Kada korinsik ponovo unese koordinate prve i treca tacke
		*  moze da se desi da se jedan od njih dve poklopi sa dugom.
		*  Zbog toga se ponovo racunaju stranice, 
		*  da bi se obezbedila veca sigurnost!
		*
		*********************************************************/
		a = sqrt(pow((x1-x2), 2)+pow((y1-y2), 2));
		b = sqrt(pow((x2-x3), 2)+pow((y2-y3), 2));
		c = sqrt(pow((x1-x3), 2)+pow((y1-y3), 2));

	 }

	/************************************************
	*
	*  Ispis duzine stranica i obima trougla
	*
	*************************************************/
	O = a+b+c;
	printf("\n\nStranica a je %.2f!\n", a);
	printf("\nStranica b je %.2f!\n", b);
	printf("\nStranica c je %.2f!\n", c);
	printf("\n Obim trougla je %.2f\n\n\n", O);

	
	/****************************************************
	*
	*  Provera da li korinsik zeli da ponovo izvrsi program
	*
	*****************************************************/
	scanf("%c", &again); /*ovo je neophodno zbog entera iz bafera tastature */
	printf("\n\nDa li zelite da ponovite program? (y/n) ");
	scanf("%c", &again);
	while (again!='y' && again!='n') {
		scanf("%c", &again); /*ovo je neophodno zbog entera iz bafera tastature */
		printf("\nUnesite vrenost 'y' za DA ili 'n' za NE!\n");
		printf("Da li zelite da ponovite program? (y/n) ");
		scanf("%c", &again);
		}

}
	/****************************************************
	*
	* Kraj programa
	*
	*****************************************************/
	printf("\nKRAJ PROGRAMA\n\n\n");
	}