C++ example: custom class type used in unordered_map

To use a custom class type as key in unordered_map, we need to overload the == operator and define custom hash function for this type. See the below example.

#include <iostream>
#include <string>
#include <unordered_map>

using namespace std;

class Student{
public:
    Student(const string& name, int age):name(name), age(age){}

    friend bool operator==(const Student& lhs, const Student& rhs){
        return lhs.name == rhs.name && lhs.age == rhs.age;
    }

    void output() const{
        cout<<"Name "<<name<<" Age "<<age<<endl;
    }

public:
    string name;
    int age;
};

struct hashStudent{
    std::size_t operator()(const Student& stu) const{
        return hash<string>()(stu.name)| (hash<int>()(stu.age)<<1);
    }
};

int main(){
    unordered_map<Student, int, hashStudent> m;
    m.emplace(Student{"John", 21}, 4);
    m.emplace(Student{"John", 12}, 3);
    m.emplace(Student{"Ann", 24}, 2);

    for(const auto& [key, val]: m){
        cout<<key.name<<" "<<key.age<<" "<<val<<endl;
    }
    return 0;
}