循环队列操作实现

/*
 该实现front始终指向当前的头结点，rear始终指向尾结点的
 下一个结点
*/
#include <stdio.h>
#include <stdlib.h>

#define MAXNUM 10
#define datatype int

typedef struct queue{
        int queue[MAXNUM];
        int front;
        int rear;
}queue;

void initqueue(queue** p)
{
        *p = (queue* )malloc(sizeof(queue));

        if(*p != NULL){
                (*p)->front = 0;
                (*p)->rear = 0;
        }
}

int emptyqueue(queue** p)
{
        int val;

        val = ((*p)->front == (*p)->rear);

        return val;
}

void enqueue(queue** p, datatype x)//将x插入队尾

{
        if(((*p)->rear+1)%MAXNUM == (*p)->front){
                printf("the queue is full\n");
                return;
        }

        (*p)->queue[(*p)->rear] = x;
        (*p)->rear = ((*p)->rear+1)%MAXNUM;
}

void delqueue(queue** p, datatype* x)//删除队列头元素，用x返回

{
        if((*p)->front == (*p)->rear){
                printf("the queue is empty\n");
                return;
        }

        *x = (*p)->queue[(*p)->front];
        (*p)->front = ((*p)->front+1)%MAXNUM;
}

void firstqueue(queue** p, datatype* x)//返回队列头元素

{
        *x = (*p)->queue[(*p)->front];
}

void prqueue(queue** p)//打印队列元素

{
        int i;

        i = (*p)->front;
        while(i != (*p)->rear){
                printf("%c", (*p)->queue[i]);
                i = (i + 1) % MAXNUM;
        }
        printf("\n");
}

int main(int argc, char** argv)
{
        queue* p;
        int c, i;

        initqueue(&p);
        printf("input queue node value:\n");
/***
        while((c = getchar()) !='\n'){
                enqueue(&p, c);
        }
***/

        prqueue(&p);

        for(i = 0; i < 3; i++){
                delqueue(&p, &c);//删除一个头元素

        }

        printf("\n");
        enqueue(&p, '*');
        enqueue(&p, '$');
        prqueue(&p);

        firstqueue(&p, &c);
        printf("first queue is %c\n", c);

        exit(0);
}