unordered_multiset

/* *********************************************************
 * KNOWLEDGE CENTER
 * st::unordered_multiset
 * Detailed Video Explanation: https://youtu.be/AdCryKn9T9o
********************************************************** */


#include <iostream>
#include <functional>
#include <unordered_set>

using namespace std;

class Student{
public:
  int id;
  string name;

  bool operator==(const Student& s) const{
    return (this->id == s.id && this->name == s.name);
  }

  void print_student() const {
    cout << "[ id = " << id << ", name = " << name << "]\n";
  }

};

class StudentHashFunction{
public:
  size_t operator()(const Student& s) const{
    return (hash<int>{}(s.id) + hash<string>{}(s.name));
  }
};

int main(){

  unordered_multiset<int> us = {5, 10, 4, 20, 5, 5, 15};
  for(int x: us)
    cout << x << " ";
  cout << endl;

  auto its = us.equal_range(5);
  for(auto it = its.first; it != its.second; ++it)
    cout << *it << " ";
  cout << endl;

  cout << "size = " << us.size() << endl;
  cout << "count(5) = " << us.count(5) << endl;
  cout << "num erased(5) " << us.erase(5) << endl;
  cout << boolalpha << "found 16 = " << (us.find(16) != us.end()) << endl;
  cout << "num buckets = " << us.bucket_count() << endl;
  cout << "load factor = " << us.load_factor() << endl;

  unordered_multiset<Student, StudentHashFunction> uss = {{50, "Simon"}, {20, "Thomas"}, {50, "Simon"}};
  for(auto& st: uss)
    st.print_student();


    return 0;
}