HackerRank C Solution - Small Triangles, Large Triangles

You are given n triangles, specifically, their sides a1, b1 and c1. Print them in the same style but sorted by their areas from the smallest one to the largest one. It is guaranteed that all the areas are different.

The best way to calculate a volume of the triangle with sides a, b and c is Heron's formula:

1. 1. #include <stdio.h>
   2. #include <stdlib.h>
   3. #include <math.h>
   5. struct triangle
   6. {
   7. int a;
   8. int b;
   9. int c;
   10. };
   12. typedef struct triangle triangle;
   13. void sort_by_area(triangle *tr, int n) {
   14. // Sort an array a of the length n
   15. int *p=malloc(n*sizeof(int));
   16. //create array of size n to store "volumes"
   17. for(int i=0;i<n;i++)
   18. {
   19. float a=(tr[i].a+tr[i].b+tr[i].c)/2.0;
   20. //use 2.0 compulsary int/int gives int, int/float gives float
   21. p[i]=(a*(a-tr[i].a)*(a-tr[i].b)*(a-tr[i].c));
   22. //formula without sqrt as areas are different guarenteed
   23. //because sqrt dosent work well with float values
   24. }
   25. //bubble sort
   26. for(int i=0;i<n;i++)
   27. {
   28. for(int j=0;j<n-i-1;j++)
   29. {
   30. if(p[j]>p[j+1])
   31. {
   32. int temp=p[j];
   33. p[j]=p[j+1];
   34. p[j+1]=temp;
   35. //swapping array of areas in ascending
   36. //and simuntaneously the structure contents
   37. temp=tr[j].a;
   38. tr[j].a=tr[j+1].a;
   39. tr[j+1].a=temp;
   40. temp=tr[j].b;
   41. tr[j].b=tr[j+1].b;
   42. tr[j+1].b=temp;
   43. temp=tr[j].c;
   44. tr[j].c=tr[j+1].c;
   45. tr[j+1].c=temp;
   46. }
   47. }
   48. }
   49. }
   50. int main()
   51. {
   52. int n;
   53. scanf("%d", &n);
   54. triangle *tr = malloc(n * sizeof(triangle));
   55. for (int i = 0; i < n; i++) {
   56. scanf("%d%d%d", &tr[i].a, &tr[i].b, &tr[i].c);
   57. }
   58. sort_by_area(tr, n);
   59. for (int i = 0; i < n; i++) {
   60. printf("%d %d %d\n", tr[i].a, tr[i].b, tr[i].c);
   61. }
   62. return 0;
   63. }