#include <iostream>

struct Node
{
    int value;
    Node* next;
};

class Iterator
{
public:
    Iterator(Node* current)
        : current {current}
    {}
        
    int& operator*()
    {
        return current->value;
    }

    Iterator& operator++()
    {
        current = current->next;
        return *this;
    }

    bool operator==(Iterator const& rhs) const
    {
        return current == rhs.current;
    }
        
private:
    Node* current;
};

class List
{
public:
    List()
        : top {}
    {}

    List(List const&) = delete;
    List& operator=(List const&) = delete;
    List(List &&) = delete;
    List& operator=(List &&) = delete;

    ~List()
    {
        while (top != nullptr)
        {
            Node* tmp {top->next};
            delete top;
            top = tmp;
        }
    }

    void add(int i)
    {
        top = new Node{i, top};
    }

    Iterator begin()
    {
        return Iterator{top};

    }

    Iterator end()
    {
        return Iterator{nullptr};
    }

private:

    Node* top;

};

int main()
{
    List list {};
    list.add(3);
    list.add(2);
    list.add(7);
    list.add(4);
    list.add(1);

    *(++list.begin()) = 12; 
    
    for (auto it {list.begin()}; !(it == list.end()); ++it)
    {
        std::cout << *it << " ";
    }
    std::cout << std::endl;
    // Expected output: 1 12 7 2 3
}