queue.cpp

来自「经典数据结构源代码」· C++ 代码 · 共 52 行

#include "../header/Queue.hpp"

template <class Type>
void Queue<Type>::destroy()
{
    while (!empty())
        pop();
}

template <class Type>
void Queue<Type>::pop()
{
    // pop is unchecked: Popping off an empty Queue is undefined
    QueueItem<Type>* p = head;
    head = head->next;         // head now points to next element
    delete p;                  // delete old head element
}

template <class Type>
void Queue<Type>::push(const Type &val)
{
    // allocate a new QueueItem object
    QueueItem<Type> *pt = new QueueItem<Type>(val);
    // put item onto existing queue
    if (empty())
        head = tail = pt; // the queue now has only one element
    else {
        tail->next = pt; // add new element to end of the queue
        tail = pt;
    }
}

template <class Type>
void Queue<Type>::copy_elems(const Queue &orig)
{
    // copy elements from orig into this Queue
    // loop stops when pt == 0, which happens when we reach orig.tail
    for (QueueItem<Type> *pt = orig.head; pt; pt = pt->next)
        push(pt->item); // copy the element
}

template <class Type>
Queue<Type>& Queue<Type>::operator=(const Queue& orig)
{
       if ( this != &orig ) {
            destroy();
            copy_elems(orig);
       }
       
       return *this;              
}