Design Patterns - Iterator

//
//  main.cpp
//  iterator
//
//  Created by Andrei Gavrila on 28/11/2021.
//  Copyright © 2021 Andrei Gavrila. All rights reserved.
//

#include <iostream>
#include <algorithm>

template <typename T>
class Node
{
public:
    Node *next;

    T value;

    Node(Node<T>* next, T value): next(next), value(value) {}
};

template <typename T>
class List
{
private:
    Node<T> *head;

public:
    struct Iterator
    {
        Iterator(Node<T> *node) : node(node) {}

        T& operator*() const { return node->value; }
        T operator->() { return node->value; }
        Iterator& operator++() { node = node->next; return *this; }
        Iterator operator++(int) { Iterator tmp = *this; ++(*this); return tmp; }

        friend bool operator== (const Iterator& a, const Iterator& b) { return a.node == b.node; };
        friend bool operator!= (const Iterator& a, const Iterator& b) { return a.node != b.node; };

    private:
        Node<T> *node;
    };

    List(): head(nullptr) {}

    void add(T value)
    {
        head = new Node<T>(head, value);
    }

    void print()
    {
        Node<T> *n = head;

        std::cout << "List: [" ;
        while (n)
        {
            std::cout << n->value << (n->next ? ", " : "");

            n = n->next;
        }
        std::cout << "]" << std::endl;
    }

    Iterator begin() {
        return Iterator(head);
    }

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

int main(int argc, const char * argv[])
{
    List<std::string> *list = new List<std::string>();

    list->add("element 1");
    list->add("element 2");
    list->add("element 3");

    list->print();

    for (auto it = list->begin(), end = list->end(); it != end; ++it) {
        const auto s = *it;

        std::cout << s << "\n";
    }

    for (auto s: *list)
    {
        std::cout << s << "\n";
    }

    List<int> *listOfInts = new List<int>();

    listOfInts->add(1);
    listOfInts->add(2);
    listOfInts->add(3);

    int sum = 0;
    for (auto n: *listOfInts)
    {
        sum += n;
    }
    std::cout << "Sum = " << sum << std::endl;

    int sum_quick = 0;
    std::for_each(listOfInts->begin(), listOfInts->end(), [&](int const& n) {sum_quick += n;});
    std::cout << "Sum = " << sum_quick << std::endl;

    return 0;
}