Как написать итератор в c++ 11?

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template
class Stack {
private:
    struct Node {
        T data;
        Node* next;
        Node(const T& data, Node* next = nullptr) : data(data), next(next) {}
    };
    Node* head;
    size_t size;
public:
    Stack() : head(nullptr), size(0) {}
    ~Stack() { while (!empty()) pop(); }
    void push(const T& data) { head = new Node(data, head); size++; }
    void pop() { if (!empty()) { Node* temp = head; head = head->next; delete temp; size--; } }
    T top() const { return head->data; }
    bool empty() const { return head == nullptr; }
    size_t getSize() const { return size; }

    // класс итератора
    class Iterator {
    private:
        Node* node;
    public:
        Iterator(Node* node) : node(node) {}
        Iterator& operator++() { node = node->next; return *this; }
        T& operator*() { return node->data; }
        bool operator!=(const Iterator& other) const { return node != other.node; }
    };

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

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Stack stack;
stack.push(1);
stack.push(2);
stack.push(3);

for (auto it = stack.begin(); it != stack.end(); ++it) {
    std::cout << *it << ' ';  // выводит: 3 2 1
}