تنفيذ Queue باستخدام Linked List في C++ دون مؤشرات معلّقة

#include <iostream>
#include <memory>
#include <optional>
#include <utility>

class LinkedQueue {
    struct Node {
        int value;
        std::unique_ptr<Node> next;
        explicit Node(int v) : value(v) {}
    };
    std::unique_ptr<Node> front;
    Node* rear = nullptr; // Non-owning observer; front owns the chain.
public:
    LinkedQueue() = default;
    LinkedQueue(const LinkedQueue&) = delete;
    LinkedQueue& operator=(const LinkedQueue&) = delete;
    bool empty() const { return !front; }
    void enqueue(int value) {
        auto node = std::make_unique<Node>(value);
        Node* newRear = node.get();
        if (rear) rear->next = std::move(node);
        else front = std::move(node);
        rear = newRear;
    }
    std::optional<int> peek() const {
        if (!front) return std::nullopt;
        return front->value;
    }
    std::optional<int> dequeue() {
        if (!front) return std::nullopt;
        auto old = std::move(front);
        front = std::move(old->next);
        if (!front) rear = nullptr;
        return old->value;
    }
    ~LinkedQueue() { while (!empty()) dequeue(); }
};

int main() {
    LinkedQueue queue;
    queue.enqueue(10);
    queue.enqueue(20);
    while (auto value = queue.dequeue()) std::cout << *value << ' ';
    queue.enqueue(30); // Reuse after removing the last node.
    if (auto value = queue.dequeue()) std::cout << *value << '\n';
    std::cout << "Empty: " << queue.empty() << '\n';
}