#include <iostream>
#include <set>
using namespace std;

class Student
{
    unsigned id;
    string name;
public:
    Student() = delete;
    Student(unsigned arg1, string arg2 = "") : id(arg1), name(arg2) {}
    Student(const Student&) = default;
    bool operator<(const Student& obj) const
    {
        return id < obj.id;
    }
    bool operator==(const Student& obj) const
    {
        return id == obj.id;
    }
    friend ostream& operator<<(ostream& out, const Student& obj)
    {
        out << obj.id << "   " << obj.name;
        return out;
    }
};

ostream& operator<<(ostream& out, const multiset<Student>& stu)
{
    for (auto it = stu.cbegin(); it != stu.cend(); ++it)
    {
        out << *it << endl;
    }
    return out;
}

int main()
{
    multiset<Student> Students;
    Students.insert({117,"John"});
    Students.insert({124,"Paul"});
    Students.insert({102,"George"});
    Students.insert({106,"Ringo"});
    Students.insert({223,"Peter"});
    Students.insert({203,"Paul"});
    Students.insert({243,"Mary"});

    cout << "Students.size() = "  << Students.size() << endl;
    cout << Students << endl;

    multiset<Student>::iterator msIt;
    msIt = Students.insert({309,"Mick"});
    cout << "New student: " << *msIt << endl;

    msIt = Students.insert({117,"Elvis"});
    cout << "Another new student: " << *msIt << endl << endl;

    cout << Students << endl;

    // Check count
    cout << "count of 117 = " << Students.count(117) << endl;
    // cout << "# of Paul = " << Students.count("Paul") << endl;  // ERROR
    cout << endl;

    // check find
    multiset<Student>::const_iterator cMsIt;
    cMsIt = Students.find(124);
    cout << "find 124: " << *cMsIt << endl;
    //  cout << *(Students.find(107)) << endl;  // ERROR
    ++cMsIt;
    cout << *cMsIt << endl;
    ++cMsIt;
    cout << *cMsIt << endl;
    int id = 125;
    cMsIt = Students.find(id);
    // cout << *cMsIt << endl; // CRASH
    if (cMsIt == Students.end())
        cout << "Can't find " << id << endl << endl;

    // equal_range
    cout << "equal_range 117" << endl;
    auto twoIterators = Students.equal_range(117);
    cout << *twoIterators.first << endl <<  *twoIterators.second << endl << endl;
    cout << "equal_range 203" << endl;
    twoIterators = Students.equal_range(203);
    cout << *twoIterators.first << endl <<  *twoIterators.second << endl << endl;
    cout << "equal_range 204" << endl;
    twoIterators = Students.equal_range(204);
    cout << *twoIterators.first << endl <<  *twoIterators.second << endl << endl;
    if (twoIterators.first == twoIterators.second) cout << "204 not found" << endl << endl;

    // erase
    cout << "Erase 117: " << Students.erase(117) << endl;
    cout << "Erase 118: " << Students.erase(118) << endl << endl;
    cout << Students << endl;
}