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  1. #include <iostream>
  2. #include <vector>
  3. #include <algorithm>
  4.  
  5. struct Object {
  6.   size_t id;
  7.   size_t state;
  8. };
  9.  
  10. struct LessByAllFields {
  11.   bool operator()(const Object &first, const Object &second) {
  12.     if (first.id == second.id) {
  13.       return first.state < second.state;
  14.     }
  15.     return first.id < second.id;
  16.   }
  17. };
  18.  
  19. struct LessById {
  20.   bool operator()(const Object &first, const Object &second) {
  21.     return first.id < second.id;
  22.   }
  23. };
  24.  
  25. std::ostream &operator<<(std::ostream &out, const Object &obj) {
  26.   return out << "id " << obj.id << " state " << obj.state << ' ';
  27. }
  28.  
  29. std::ostream &operator<<(std::ostream &out,
  30.                          const std::vector<Object> &objects) {
  31.   for (auto object : objects) {
  32.     out << object << ' ';
  33.   }
  34.   return out << '\n';
  35. }
  36.  
  37. template <typename Comp>
  38. std::vector<Object> UniqueInFirst(const std::vector<Object> &first,
  39.                                   const std::vector<Object> &second,
  40.                                   Comp comp) {
  41.   std::vector<Object> unique_in_first;
  42.   std::set_difference(second.begin(), second.end(), first.begin(), first.end(),
  43.                       std::back_inserter(unique_in_first), comp);
  44.   return unique_in_first;
  45. }
  46.  
  47. template <typename Comp>
  48. std::vector<Object> Intersection(const std::vector<Object> &first,
  49.                                  const std::vector<Object> &second, Comp comp) {
  50.   std::vector<Object> unique_in_first;
  51.   std::set_intersection(first.begin(), first.end(), second.begin(),
  52.                         second.end(), std::back_inserter(unique_in_first),
  53.                         comp);
  54.   return unique_in_first;
  55. }
  56.  
  57. int main() {
  58.   std::vector<Object> old = {{0, 0}, {1, 1}, {2, 2}, {3, 3}};
  59.   std::vector<Object> current = {{4, 4}, {0, 0}, {2, 3}, {3, 5}};
  60.  
  61.   std::sort(old.begin(), old.end(), LessByAllFields());
  62.   std::sort(current.begin(), current.end(), LessByAllFields());
  63.  
  64.   std::cout << "Old vector             : " << old;
  65.   std::cout << "Current vector         : " << current;
  66.   std::cout << "Only new elements      : " << UniqueInFirst(old, current,
  67.                                                             LessByAllFields());
  68.   std::cout << "Only old elements      : " << UniqueInFirst(current, old,
  69.                                                             LessByAllFields());
  70.   std::cout << "Same with state changed: \n"
  71.             << "in old: " << Intersection(old, current, LessById())
  72.             << "in new: " << Intersection(current, old, LessById());
  73. }
  74.  
Success #stdin #stdout 0s 3276KB
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stdin
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Standard input is empty
stdout
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Old vector             : id 0 state 0  id 1 state 1  id 2 state 2  id 3 state 3  
Current vector         : id 0 state 0  id 2 state 3  id 3 state 5  id 4 state 4  
Only new elements      : id 2 state 3  id 3 state 5  id 4 state 4  
Only old elements      : id 1 state 1  id 2 state 2  id 3 state 3  
Same with state changed: 
in old: id 0 state 0  id 2 state 2  id 3 state 3  
in new: id 0 state 0  id 2 state 3  id 3 state 5
https://ideone.com/D5IHF9
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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