队列的实现—由链表实现

#include <stdio.h>
#include <stdlib.h>

typedef int datatype;

typedef struct _node_
{
 datatype data;
 struct _node_ *next;
} linknode, *linklist;

typedef struct
{
 linklist front;
 linklist rear;
} linkqueue;

linkqueue *CreateEmptyQueue()
{
 linkqueue *lq;

 lq = (linkqueue *)malloc(sizeof(linkqueue));
 lq->front = lq->rear = (linklist)malloc(sizeof(linknode));
 lq->front->next = NULL;

 return lq;
}

int EmptyQueue(linkqueue *lq)
{
 return (lq->front == lq->rear);
}

void EnQueue(linkqueue *lq, datatype x)
{
 lq->rear->next = (linklist)malloc(sizeof(linknode));
 lq->rear = lq->rear->next;
 lq->rear->data = x;
 lq->rear->next = NULL;

 return;
}

datatype DeQueue(linkqueue *lq)
{
 linklist q;

 q = lq->front;
 lq->front = q->next;
 free(q);

 return (lq->front->data);
}

void ClearQueue(linkqueue *lq)
{
 linklist q;

 while (lq->front != lq->rear)
 {
  q = lq->front;
  lq->front = q->next;
  free(q);
 }

 return;
}