c语言编程之循环队列

        利用链表实现的循环队列，完成了队列的入队和出队，对于队空和队满用了一个flag进行标记。入队flag++,出队flag--

  1 #include"stdio.h"
  2 
  3 typedef int element;
  4 
  5 typedef struct Node{
  6         struct Node *next;
  7         element data;
  8 }*pNode;
  9 
 10 typedef struct QNode{
 11         pNode front,rear;
 12         element flag;
 13 }*Linknode;
 14 
 15 //init a empty queue
 16 element Init_queue(Linknode *pLinknode)
 17         {
 18            Linknode P;
 19            P=*pLinknode;
 20            P->front=P->rear=(pNode)malloc(sizeof(struct Node));
 21            P->front->next=NULL;
 22            P->rear->next=P->front;     // make loop queue font linked rear,in usuall queue this is P->rear->next=NULL;make a change become 
//Loop queue;
 23            P->flag=0;
 24         }
 25 
 26 //add a data to queue rear
 27 element Add_queue(Linknode *pLinknode,int num)
 28         {
 29           Linknode P;
 30           P=*pLinknode;
 31           pNode s=(pNode)malloc(sizeof(struct Node));
 32           s->data=num;
 33           s->next=P->front;   //in this position we can see the new add memory s is point to front,in usuall queue we can see s->next=NULL;

 34           P->rear->next=s;
 35           P->rear=s;                   
 36           ++P->flag;
 37           printf("add data:%d add flag:%d\n",P->rear->data,P->flag);
 38         }
 42         {
 43           if((*pLinknode)->flag==0)
 44                 {
 45                   printf("queue is empty\n");
 46                   return 0;
 47                 }
 48           //if(((*pLinknode)->front)==((*pLinknode)->rear))
 49           //    {
 50           //            printf("queue is empty!!");
 51           //            return 0;
 52           //      }
 53           Linknode P;
 54           pNode k;
 55           P=*pLinknode;
 56           k=P->front->next;
 57           P->front->next=k->next;
 58           printf("delet data:%d\n",k->data);
 59           //--P->flag;
 60           free(k);
 61           printf("delete flag:%d\n",P->flag);
 62           --P->flag;
 63           return 0;
 64         }
 65 
 66 element Print_queue(Linknode pLinknode)
 67         {
 68           pNode p;
 69           p=pLinknode->front;
 71           while(p!=pLinknode->rear&&pLinknode->flag)    //it is importand,because in loop queue fornt==rear can means empty or full,it is a                                                  //loop,we can't determin this loop queue is empty by using front==rear,must add num as flag;

 72                 {
 73                   p=p->next;
 74                   printf("data:%d\n",p->data);
 75                 }
 76           return 0;
 77         }
 78 element main()
 79         {
 80           Linknode pQnode;
 81           pQnode=(Linknode)malloc(sizeof(struct QNode));
 82           Init_queue(&pQnode);
 83           Add_queue(&pQnode,99);
 84           Add_queue(&pQnode,11);
 85           Add_queue(&pQnode,22);
 86           Add_queue(&pQnode,33);
 87           Add_queue(&pQnode,44);
 88           Add_queue(&pQnode,55);
 89           Print_queue(pQnode);
 90           Delet_queue(&pQnode);
 91           Delet_queue(&pQnode);
 92           Delet_queue(&pQnode);
 93           Delet_queue(&pQnode);
 94           Delet_queue(&pQnode);
 95           Delet_queue(&pQnode);
 96           Delet_queue(&pQnode);
 97           Print_queue(pQnode);
 98           return 0;
 99         }
100