ch2/exercises1/ex10.c

   1 /* to check whether all the three points lie on a straight line */
   2
   3 #include<stdio.h>
   4
   5 int main()
   6 {
   7         int x1,y1,x2,y2,x3,y3;
   8         float area;
   9         printf("Enter X1,Y1:");
  10         scanf("%d %d",&x1,&y1);
  11
  12         printf("Enter X2,Y2:");
  13         scanf("%d %d",&x2,&y2);
  14
  15         printf("Enter X3,Y3:");
  16         scanf("%d %d",&x3,&y3);
  17
  18         /*compute the area formed by these three points. if
  19         it is zero , then they all lie on a same line i.e they don form a triangle */
  20         area = (1/2)*((x1*(y2-y3))+(x2*(y3-y1))+(x3*(y1-y2)));
  21
  22         if(area == 0)
  23                 printf("They lie on a straight line\n");
  24         else
  25                 printf("They dont lie on a straight line\n");
  26
  27         printf("Press any key to exit\n");
  28         getch();
  29         return 0;
  30 }