#include template class Queue { public: Queue(); ~Queue(); void enqueue(T value); T dequeue(); void clear(); inline T peek() const; inline bool isEmpty() const; private: Queue(const Queue& q); Queue& operator=(const Queue& q); struct node { T value; node *next; } *head, *tail; template friend std::ostream& operator<<(std::ostream& os, const Queue& queue); }; int main() { using std::cout; using std::endl; using std::cin; try { Queue q; size_t number; cin >> number; for(; number != 0; number--) { q.enqueue(number); } cout << "current queue: " << endl << q << endl << endl; q.dequeue(); q.dequeue(); cout << "queue after dequeueing two elements: " << endl << q << endl; q.clear(); cout << endl << "queue after cleaning: " << endl << q << endl; q.enqueue(777); cout << endl << "queue after insertion of one element: " << endl << q << endl; } catch(const char *msg) { cout << msg << endl; } return 0; } template Queue::Queue():head(nullptr), tail(nullptr) {} template Queue::~Queue() { clear(); } template void Queue::enqueue(T value) { node *tmp = new node; tmp->value = value; tmp->next = nullptr; if(isEmpty()) { head = tail = tmp; } else { tail->next = tmp; tail = tmp; } } template T Queue::dequeue() { if(isEmpty()) { throw "Queue is empty"; } node *tmp = head; int value = head->value; head = head->next; delete tmp; return value; } template inline T Queue::peek() const { if(isEmpty()) { throw "Queue is empty"; } return head->value; } template inline bool Queue::isEmpty() const { return !head; } template void Queue::clear() { while(!isEmpty()) { node *tmp = head; head = head->next; delete tmp; } head = nullptr; } template std::ostream& operator<<(std::ostream& os, const Queue& q) { auto tmp = q.head; while(tmp) { os << tmp->value << " "; tmp = tmp->next; } return os; }

Queue class template