jul_2_2015.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>

typedef struct trougao{
  double ax, ay;
  double bx, by;
  double cx, cy;
} TROUGAO;

double duzina(double ax, double ay, double bx, double by){
  return sqrt((ax-bx)*(ax-bx)+(ay-by)*(ay-by));
}


double povrsina(TROUGAO t){
  double s;
  double d1,d2,d3;
  d1=duzina(t.ax,t.ay,t.bx, t.by);
  d2=duzina(t.ax,t.ay,t.cx, t.cy);
  d3=duzina(t.cx,t.cy,t.bx, t.by);
  s=(d1+d2+d3)/2;
  return sqrt(s*(s-d1)*(s-d2)*(s-d3));
}

int poredi (const void *a, const void *b){
 TROUGAO x=*(TROUGAO*)a;
 TROUGAO y=*(TROUGAO*)b;
 double px,py;
 px=povrsina(x);
 py=povrsina(y);
 if(px>py)
   return -1;
 else if(px<py)
   return 1;
 else
   return 0;
}

int main () {

  int n,i;
  FILE *ulaz;

  ulaz= fopen ("trouglovi.txt", "r");
  if(ulaz==NULL){
    printf("Greska.\n");
    exit(EXIT_FAILURE);
  }


  TROUGAO *t;

  fscanf(ulaz,"%d", &n);
  if(n<=0){
    fprintf(stderr, "Greska aha greska.\n");
    exit(EXIT_FAILURE);
  }

  t=malloc(n*sizeof(TROUGAO));
  if(t==NULL){
    printf("Neuspesna alokacija.\n");
    exit(EXIT_FAILURE);
  }

  for(i=0; i<n; i++){
    fscanf(ulaz, "%lf%lf%lf%lf%lf%lf", &t[i].ax, &t[i].ay, &t[i].bx,&t[i].by, &t[i].cx, &t[i].cy);
  }

  qsort(t,n, sizeof(TROUGAO), &poredi);

  for(i=0; i<n ;i++){
    printf("%.2lf %.2lf %.2lf %.2lf %.2lf %.2lf\n\n", t[i].ax, t[i].ay,t[i].bx,t[i].by, t[i].cx, t[i].cy);
  }

  free(t);
  exit(EXIT_SUCCESS);
}