queue.hpp

来自「经典数据结构源代码」· HPP 代码 · 共 42 行

#ifndef QUEUE_HPP
#define QUEUE_HPP

// declaration that Queue is a template needed for friend declaration in QueueItem
template <class Type> class Queue;

template <class Type>
class QueueItem {
	friend class Queue<Type>;
	// private class: no public section
	QueueItem(const Type &t): item(t), next(0) { }
	Type item;           // value stored in this element
	QueueItem *next;     // pointer to next element in the Queue
};

template <class Type>
class Queue {
public:
	// empty Queue
	Queue(): head(0), tail(0) { }
	// copy control to manage pointers to QueueItems in the Queue
	Queue(const Queue &Q): head(0), tail(0) { copy_elems(Q); }
	Queue& operator=(const Queue&);
	~Queue() { destroy(); }
	// return element from head of Queue
	// unchecked operation: front on an empty Queue is undefined
	Type& front() { return head->item; }
	const Type &front() const { return head->item; }
	void push(const Type &);       // add element to back of Queue
	void pop ();                   // remove element from head of Queue
	// true if no elements in the Queue
	bool empty () const { return head == 0; }
private:
	QueueItem<Type> *head;         // pointer to first element in Queue
	QueueItem<Type> *tail;         // pointer to last element in Queue
	// utility functions used by copy constructor, assignment, and destructor
	void destroy();                // delete all the elements
	void copy_elems(const Queue&); // copy elements from parameter
};

#endif