栈与队列：循环队列算法+可执行代码

//队列顺序存储结构
//取模运算：就是取余数，它的值永远不会大于除数
(rear+1)%QueueSize
(front+1)%QueueSize
//队列的顺序存储结构
#define MAXSIZE 100
typedef struct
{
    ElemType *base; //用于存放内存分配基地址
                     //也可用于数组存放 
    int front;
    int rear; 
}cy

initQueue(cycleQueue *q)
{
    q->base = (ElemType *)malloc(MAXSIZE * sizeof(ElemType));
    if(!q->base)
    exit(0);
    q->front = q->rear = 0; //指向0号单元 
} 

InsertQueue(cycleQueue *q, ElemType e)
{
    if((q->rear+1)%MAXSIZE == Q->front)
    return;//队列已满
    q->base[q->rear] = e;
    q->rear = (q->rear+1)%MAXSIZE; 
}

DeleteQueue(cycleQueue *q, ElemType *e)
{
    if(q->front == q->rear)
    return;//队列为空
    *e = q->base[q->front];
    q->front = (q->front+1)%MAXSIZE; 
} 


//循环队列可执行代码
#include<stdio.h>
#include<stdlib.h>

#define MAXQSIZE 100 //最大长度 
#define OVERFLOW 0
#define ERROR -1
#define OK 1

typedef int SElemType;
typedef int QElemType;
typedef int Status;
typedef struct
{
    QElemType *base;  //储存空间的基地址 
    int front;
    int rear;
}sqQueue;

Status InitQueue(sqQueue *Q); //初始化
int QueueLength(sqQueue Q); //测量长度
Status EnQueue(sqQueue *Q, QElemType e);//入队列
Status DeQueue(sqQueue *Q, QElemType *e);//出队列
SElemType GetHead(sqQueue Q)//获取头顶元素

Status InitQueue(sqQueue *Q)
{
    Q->base = (QElemType *)malloc(sizeof(QElemType)*MAXQSIZE);
    if(!Q->base)
    exit(OVERFLOW);
    Q->front = Q->rear = 0;
    return OK;
}

int QueueLength(sqQueue Q)
{
    return (Q.rear-Q.front+MAXQSIZE)%MAXQSIZE;
}

Status EnQueue(sqQueue *Q, QElemType e)
{
    if((Q->front+1)%MAXQSIZE == Q->front)  //判断对是否已满
    return ERROR;
    Q->base[Q->rear] = e;
    Q->rear = (Q->rear+1)%MAXQSIZE;
    return OK; 
}

Status DeQueue(sqQueue *Q, QElemType *e)
{
    if(Q->front == Q->rear) 
    {
        return ERROR;
    }
    *e = Q->base[Q->front];
    Q->front = (Q->front+1)%MAXQSIZE;
    return OK;
}

SElemType GetHead(sqQueue Q)
{
    if(Q.front != Q.rear)
    return Q.base[Q.front];
}

int main(void)
{
    sqQueue q;
    int e;
    int len;
    int ehead;
    
    InitQueue(&q);
    printf("请输入队列元素 以0结束输入：\n"); 
    scanf("%d",&e);
    while(e != 0)
    {
        EnQueue(&q,e);
        scanf("%d",&e);
    }
    
    len = QueueLength(q);
    printf("队列的长度是： %d\n",len);
    
    ehead = GetHead(q);
    printf("队列的头顶元素是：%d\n",ehead);
    
    printf("队列中的元素是：\n"); 
    while(q.front != q.rear)
    {
        DeQueue(&q,&e);
        printf("%d ",e);
    }
    
    return 0;
}