队列

template<class Elem>
//用数组实现的队列
class AQueue:public Queue<Elem>
{
private:
    int size;
    int front;
    int rear;
    Elem *listArray;
public:
    AQueue(int sz=DefaultListSize)
    {
        size=sz+1;
        rear=0;front=1;
        listArray=new Elem[size];
    }
    ~AQueue()
    {
        delete [] listArray;
    }
    void clear()
    {
        front=rear;
    }
    bool enqueue(const Elem& it)
    {
        if(((rear+2)%size)==front) return false;
        rear=(rear+1)%size;
        listArray[rear]=it;
        return true;
    }
    bool dequeue(Elem & it)
    {
        if(length()==0) return false;
        it=listArray[front];
        front=(front+1)%size;
        return true;
    }
    bool frontValue(Elem & it) const
    {
        if(length()==0) return false;
        it=listArray[front];
        return true;
    }
    virtual int length() const
    {
        return ((rear+size)-front+1)%size;
    }
};


#include "LList.h"
template<class Elem>
//用链表实现的队列
class LQueue:public Queue<Elem>
{
private:
    Link<Elem> *front;
    Link<Elem> *rear;
    int size;
public:
    LQueue(int sz=DefaultListSize)
    {
        front=NULL;rear=NULL;size=0;
    }
    ~LQueue()
    {
        clear();
    }
    void clear()
    {
        while(front!=NULL)
        {
            rear=front;
            front=front->next;
            delete rear;
        }
        rear=NULL;
        size=0;
    }
    bool enqueue(const Elem & it)
    {
        if(rear==NULL)
            front =rear=new Link<Elem>(it,NULL);
        else
        {
            rear->next=new Link<Elem>(it,NULL);
            rear=rear->next;
        }
        size++;
        return true;
    }
    
    bool dequeue(Elem &it)
    {
        if(size==0) return false;
        it=front->element;
        Link<Elem>* ltemp=front;
        front=front->next;
        delete ltemp;
        if(front==NULL)
            rear=NULL;
        size--;
        return true;
    }

    bool frontValue(Elem & it) const
    {
        if(size==0) return false;
        it=front->element;
        return true;
    }
    virtual int length() const
    {
        return size;
    }
};