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