链式队列

#include <cstdio>
#include <conio.h>
#include <windows.h>
typedef char ElemType;

typedef struct QNode
{
   ElemType data;
   struct QNode *next;   
}QNode,*QueuePtr;

typedef struct
{
   QueuePtr front;   //队头指针 
   QueuePtr rear;    //队尾指针 
}LinkQueue;

//创建一个队列 
void initQueue(LinkQueue *q)
{
   q->front = q->rear = (QueuePtr)malloc(sizeof(QNode));    //初始化一个空队列
   if(!q->front)  exit(0);
   q->front->next = NULL;   //头指针置NULL 
}

//入队列
void EnQueue(LinkQueue *q,ElemType e)
{
   QueuePtr p;
   p = (QueuePtr)malloc(sizeof(QNode));   //创建一个队列元素结点 
   if(!q->front)  exit(0);
   p->data = e;
   p->next = NULL;
   q->rear->next = p;   //原本的队尾next指针指向新的结点 
   q->rear = p;         //插入数据 
}

//出队列
void DeQueue(LinkQueue *q,ElemType *e)
{
   QueuePtr p;
   if(q->front == q->rear) return;  //队列空，返回 
   p = q->front->next;
   *e = p->data;
   q->front->next = p->next;
   if(q->rear == p)  q->rear = q->front;  //如果队头就是队尾，则修改队尾指针 
   free(p);   
}

//销毁一个队列
void DestroyQueue(LinkQueue *q)
{
   while(q->front)
      {
         q->rear = q->front->next;
         free(q->front);
         q->front = q->rear;   
      }   
} 

int main()
{
   ElemType e;
   LinkQueue q;
   initQueue(&q);    //初始化队列 
   printf("Please input a string into a queue\n");
   scanf("%c",&e);
   while(e!='@')
      {
         EnQueue(&q,e);    //向队列输入 
         scanf("%c",&e);   
      }
   printf("The string into the queue is\n");
   while(q.front != q.rear)   //出列 
      {
         DeQueue(&q,&e);
         printf("%c",e);   
      }
   printf("\n");
   system("pause>nul");
   return 0;
}