fork download
copy 
  1. #include <iostream>
  2. #include <cstdlib>
  3.  
  4. struct Data
  5. {
  6.    int key;
  7.    int original_index;
  8. };
  9.  
  10. bool compare_with_itself_called = false;
  11. bool pointer_order_changed = false;
  12.  
  13. int compare(const void *p1, const void *p2)
  14. {
  15.    if(p1==p2)
  16.    {
  17.       compare_with_itself_called = true;
  18.       return 0;
  19.    }
  20.    const Data *d1 = (const Data*)p1;
  21.    const Data *d2 = (const Data*)p2;
  22.    if(d1->key < d2->key)
  23.      return -1;
  24.    if(d2->key < d1->key)
  25.      return 1;
  26.    bool index_cond = d1->original_index<d2->original_index;
  27.    bool ptr_cond = (p1<p2);
  28.    if(index_cond!=ptr_cond)
  29.    {
  30.       pointer_order_changed = true;
  31.    }
  32.    return index_cond ? -1 : 1;
  33. }
  34.  
  35. void outputArray(Data d[], unsigned n)
  36. {
  37.    for(unsigned i=0; i!=n; ++i)
  38.       std::cout << d[i].key << "@" << d[i].original_index << std::endl;
  39. }
  40.  
  41. int main()
  42. {
  43.    const unsigned N = 4;
  44.    Data array[N] = { { 8, 0 }, { 8, 1 }, { 1, 2 }, { 1, 3 } };
  45.    qsort(array, N, sizeof(Data), compare);
  46.    outputArray(array, N);
  47.    std::cout << std::endl << "compare_with_itself_called="
  48.       << (compare_with_itself_called ? "true" : "false") << std::endl;
  49.    std::cout << "pointer_order_changed="
  50.       << (pointer_order_changed ? "true" : "false") << std::endl;
  51.    return 0;
  52. }
Success #stdin #stdout 0s 4520KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
1@2
1@3
8@0
8@1

compare_with_itself_called=false
pointer_order_changed=false
https://ideone.com/l026kM
language:
C++ (gcc 8.3)
created:
7 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!