数据结构——循环队列

#include<iostream>
#include<stdlib.h>
using namespace std;

typedef int QElemType;
typedef int Status;
#define MAXSIZE 10
#define OVERFLOW -2
#define OK 1
#define ERROR 0

//循环队列的存储结构
typedef struct
{
    QElemType *base;    //存储空间的基地址
    int front;          //头指针
    int rear;           //尾指针
}SqQueue;

//循环队列的初始化
Status InitQueue(SqQueue &Q)
{
    Q.base = new QElemType[MAXSIZE];  //为队列分配一个最大容量为MAXSIZE的数组空间

    if (!Q.base)                     //分配失败
        exit(OVERFLOW);

    Q.front = Q.rear = 0;               //头指针和尾指针置为0，对列为空

    return OK;
}

//队列长度
int QueueLength(SqQueue Q)
{
    return (Q.rear - Q.front + MAXSIZE) % MAXSIZE;    //循环队列，取余
}

//入队
//插入元素e，作为队列Q的新的队尾元素
Status EnQueue(SqQueue &Q, QElemType e)
{
    if ((Q.rear + 1) % MAXSIZE == Q.front)     //尾指针在循环意义上加1后等于头指针，表明对满
        return ERROR;

    Q.base[Q.rear] = e;                   //新元素插入队尾

    Q.rear = (Q.rear + 1) % MAXSIZE;          //队尾指针加1

    return OK;
}

//出队
//删除Q的队头元素，用e返回其值
Status DeQueue(SqQueue &Q, QElemType &e)
{
    if (Q.front == Q.rear)     //队空
        return ERROR;

    e = Q.base[Q.front];      //保存队头元素

    Q.front = (Q.front + 1) % MAXSIZE;    //出队，队头指针加1

    return OK;
}

//取队头元素
//返回队头元素，不修改头指针
QElemType GetHead(SqQueue Q)
{
    if (Q.front != Q.rear)     //队列非空
        return Q.base[Q.front];
}

int main()
{
    int i, e;
    int len;
    SqQueue Q;

    InitQueue(Q);   //初始化一个空队列

    for (i = 0; i < MAXSIZE; i++)
        EnQueue(Q, i);       //入队

    len = QueueLength(Q);

    cout << "当前队列情况为：";

    for (i = Q.front; i < Q.rear; i++)
    {
        cout << Q.base[i] << " ";
    }
    cout << endl;

    cout << "当前队列里的元素有" << len << "个" << endl;

    cout << "当前的队头元素是：" << GetHead(Q) << endl;

    cout << "出队元素有：";
    for (i = 0; i < 3; i++)
    {
        DeQueue(Q, e);   //出队
        cout << e << " ";
    }
    cout << endl;

    len = QueueLength(Q);

    cout << "当前队列情况为：";

    for (i = Q.front; i < Q.rear; i++)
    {
        cout << Q.base[i] << " ";
    }
    cout << endl;

    cout << "当前队列里的元素有" << len << "个" << endl;

    cout << "当前的队头元素是：" << GetHead(Q) << endl;

    system("pause");
        return 0;
}