链队列

#include<iostream.h>
#include<stdlib.h>
#define OK    1
#define OVERFLOW  -2
#define ERROR  0
typedef int Status;
typedef int QElemType;

typedef struct QNode
{
    //结点类型
    QElemType      data;
    struct QNode     *next;
}QNode,*QueuePtr;

typedef struct
{
    //链队列类型
    QueuePtr    front;       //队头指针
    QueuePtr    rear;        //队尾指针
}LinkQueue;

Status InitQueue(LinkQueue &Q)
{
    //构造一个空队列Q
    Q.front=Q.rear=new QNode;
    if(!Q.front)
        exit(OVERFLOW);        //存储分配失效
    Q.front->next=NULL;
    return OK;
}

int QueueEmpty(LinkQueue &Q)
{
    return Q.front==NULL;
}

//取队头元素
int GetFront(LinkQueue &Q,QElemType &x)
{
    QNode *p;
    if(QueueEmpty(Q))
        return 0;
    p=Q.front->next;
    x=p->data;
}

Status EnQueue(LinkQueue &Q,QElemType e)
{
    //插入元素e为Q的新的队尾元素
    QNode *p;
    p=new QNode;
    if(!p)
        exit(OVERFLOW);        //存储分配失效
    p->data=e;
    p->next=NULL;
    Q.rear->next=p;
    Q.rear=p;
    return OK;
}

Status DeQueue(LinkQueue &Q,QElemType &e)
{
    //若队列不空，则删除Q的队头元素，
    //用e返回其值，并返回OK; 否则返回ERROR
    QNode *p;
    if(Q.front==Q.rear)
        return ERROR;
    p=Q.front->next;
    e=p->data;
    Q.front->next=p->next;
    if(Q.rear==p)
        Q.rear=Q.front;
    delete p;
    return OK;
} 

void CreateQueue(LinkQueue &Q,int n)
{
    QElemType e;
    cout<<"input n(e)=";
    for(int i=1;i<=n;i++)
    {
        cin>>e;
        EnQueue(Q,e);
    }
}

void VisitQueue(LinkQueue Q)
{
    QNode *p=Q.front->next;
    while(p)
    {
        cout<<p->data<<"  ";
        p=p->next;
    }
    cout<<endl;
}


void main()
{
    LinkQueue Q;
    int n;
    QElemType x;
    InitQueue(Q);
    cout<<"input n=";
    cin>>n;
    CreateQueue(Q,n);
    VisitQueue(Q);

    if(GetFront(Q,x))
        cout<<x<<endl;

    cout<<"input x=";
    cin>>x;
    if(EnQueue(Q,x))
        VisitQueue(Q);

    cout<<"DeQueue\n";
    if(DeQueue(Q,x))
        VisitQueue(Q);
    else
        cout<<"Queue is Empty\n";
}