队列（二）

二、链队列

        用链表表示的队列简称为链队列。

        设置一个队头指针front和一个队尾指针rear，队头指针始终指向头结点，队尾指针指向最后一个元素。空的链队列的

        队头指针和队尾指针均指向头结点。

        

                                                                                链队列示意图

        数据结构定义：

                 typedef  struct  node

                {

                        QueueElementType  data ;

                        struct  node  *next;

                }LinkQueueNode;

                typedef  struct  _LinkQueue

                {

                        LinkQueueNode *front;

                        LinkQueueNode *rear;

                }LinkQueue;

        基本操作：

                （1）初始化

                        int InitQueue(LinkQueue *Q)

                        {

                                Q->front = (LinkQueueNode *)malloc(sizeof(LinkQueueNode));

                                if(Q->front == NULL)

                                {

                                        return FALSE;

                                }

                                Q->rear = Q->front;

                                Q->front->next = NULL；

                                return TRUE;

                        }

                （2）入队

                        int EnterQueue(LinkQueue *Q,QueueElementType x)

                        {

                                LinkQueueNode *newNode;

                                newNode = (LinkQueueNode*)malloc(sizeof(LinkQueueNode));

                                if(newNode == NULL)

                                {

                                            return FALSE;        

                                }

                                newNode->data = x;

                                newNode->next = NULL;

                                Q->rear->next = newNode;

                                Q->rear = newNode;

                                return TRUE;

                        }

                （3）出队

                        int DeleteQueue(LinkQueue *Q,QueueElementType *x)

                        {

                                 LinkQueueNode *p;

                                 if(Q->front == Q->rear)

                                  {

                                          return FALSE;  

                                  }

                                  p = Q->front->next;    

                                  Q->front->next = p->next;

                                  if(Q->rear == p)     //如果队中只有一个元素p，则p出对后成为空队

                                  {

                                            Q->rear = Q->front;

                                  }

                                  *x = p->data;

                                  free(p);

                                  return TRUE;

                        }