队列实现

#include "stdio.h"  
#include "stdlib.h"  

#define OK 1  
#define ERROR 0  
#define OVERFLOW -2  

typedef char elemType;
typedef struct _QNode{
    elemType data;
    struct _QNode *next;
}QNode;
typedef struct{
    QNode *front;
    QNode *rear;
}LinkQueue;

int InitQueue(LinkQueue *q){
    q->front = q->rear = (QNode *)malloc(sizeof(QNode));
    if(!q->front)
        exit(OVERFLOW);
    q->front->next = NULL;
    return OK;    
}

int DestroyQueue(LinkQueue *q){
    while(q->front){
        q->rear = q->front->next;
        free(q->front);
        q->front = q->rear;
    }
    return OK;
}

int EnQueue(LinkQueue *q,elemType e){
    QNode *p = (QNode *)malloc(sizeof(QNode));
    if(!p)
        exit(OVERFLOW);
    p->data = e;
    p->next = NULL;
    q->rear->next = p;
    q->rear = p;  //将p插在队尾之后让p成为rear
    return OK;
}

int DeQueue(LinkQueue *q){
    QNode *p = q->front->next;
    if(q->front == q->rear)
        return ERROR;
    printf("已删除队头元素%c\n",p->data);
    q->front->next = p->next;
    if(q->rear == p)
        q->rear = q->front;
    return OK;
}

void TraverseQueue(LinkQueue *q){
    QNode *p = q->front->next;
    if(q->front == q->rear)
        printf("队列为空！\n");
    else{
        printf("队列中的元素为:\n");
        while(p != q->rear){
            printf(" %c",p->data);
            p = p->next;
        }
        printf(" %c",q->rear->data);
        printf("\n");
    }
}

void main(){  
    LinkQueue *q = (LinkQueue *)malloc(sizeof(LinkQueue));  
    InitQueue(q);  
    TraverseQueue(q);  
    printf("队尾插入元素.....\n");  
    EnQueue(q,'a');  
    EnQueue(q,'b');  
    EnQueue(q,'c');  
    EnQueue(q,'d');  
    TraverseQueue(q);  
    printf("删除队首元素...\n");  
    DeQueue(q);  
    TraverseQueue(q);  
    getchar();
}