循环队列实现(通过设置标志位tag位判断空队满队)

#include 
#include 
#include 

#define OK 1
#define ERROR 0
#define OVERFLOW 0
#define QElemType int
#define MAXQSIZE 6
using namespace std;
typedef struct
{
    QElemType *base;
    int qFront;
    int qRear;
    int tag = 0;
} SqQueue;
//初始化
int init_queue(SqQueue &sq)
{
    sq.base = (QElemType*)malloc(MAXQSIZE*sizeof(QElemType));
    if(!sq.base)
    {
        exit(OVERFLOW);
    }
    sq.qFront = sq.qRear = 0;
    return OK;
}
//队列长度
int length_queue(SqQueue sq)
{
    if(sq.tag == 1)
    {
        return MAXQSIZE;
    }
    return (sq.qRear - sq.qFront + MAXQSIZE)%MAXQSIZE;
}
//进队列
int en_queue(SqQueue &sq,QElemType e)
{
    if(length_queue(sq)==MAXQSIZE)
    {
        return ERROR;
    }

    sq.base[sq.qRear] = e;

    sq.qRear = (sq.qRear+1)%MAXQSIZE;
    if(sq.qFront == sq.qRear&&sq.tag == 0)
    {
        sq.tag = 1;
    }
    return OK;
}
//出队列
int de_queue(SqQueue &sq,QElemType &e)
{
    if(length_queue(sq)==0)
    {
        return ERROR;
    }

    e = sq.base[sq.qFront];
    sq.qFront = (sq.qFront+1)%MAXQSIZE;
    sq.tag = 0;
    return OK;
}

int main()
{
    SqQueue sq;
    init_queue(sq);
    QElemType e=1;
    en_queue(sq,e);
    en_queue(sq,e);
    en_queue(sq,e);
    en_queue(sq,e);
    en_queue(sq,e);
    en_queue(sq,e);
    en_queue(sq,e);
    en_queue(sq,e);
    en_queue(sq,e);
    en_queue(sq,e);
    cout<