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--

   #include"stdio.h"

   typedef int element;

   typedef struct Node{
           struct Node *next;
           element data;
   }*pNode;

  typedef struct QNode{
          pNode front,rear;
          element flag;
  }*Linknode;

  //init a empty queue
  element Init_queue(Linknode *pLinknode)
          {
             Linknode P;
             P=*pLinknode;
             P->front=P->rear=(pNode)malloc(sizeof(struct Node));
             P->front->next=NULL;
             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;
             P->flag=;
          }

  //add a data to queue rear
  element Add_queue(Linknode *pLinknode,int num)
          {
            Linknode P;
            P=*pLinknode;
            pNode s=(pNode)malloc(sizeof(struct Node));
            s->data=num;
            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;

           P->rear->next=s;
            P->rear=s;
            ++P->flag;
            printf("add data:%d add flag:%d\n",P->rear->data,P->flag);
          }
          {
            if((*pLinknode)->flag==)
                  {
                    printf("queue is empty\n");
                    return ;
                  }
            //if(((*pLinknode)->front)==((*pLinknode)->rear))
            //    {
            //            printf("queue is empty!!");
            //            return 0;
            //      }
            Linknode P;
            pNode k;
            P=*pLinknode;
            k=P->front->next;
            P->front->next=k->next;
            printf("delet data:%d\n",k->data);
            //--P->flag;
            free(k);
            printf("delete flag:%d\n",P->flag);
            --P->flag;
            return ;
          }

  element Print_queue(Linknode pLinknode)
          {
            pNode p;
            p=pLinknode->front;
            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;

                 {
                    p=p->next;
                    printf("data:%d\n",p->data);
                  }
            return ;
          }
  element main()
          {
            Linknode pQnode;
            pQnode=(Linknode)malloc(sizeof(struct QNode));
            Init_queue(&pQnode);
            Add_queue(&pQnode,);
            Add_queue(&pQnode,);
            Add_queue(&pQnode,);
            Add_queue(&pQnode,);
            Add_queue(&pQnode,);
            Add_queue(&pQnode,);
            Print_queue(pQnode);
            Delet_queue(&pQnode);
            Delet_queue(&pQnode);
            Delet_queue(&pQnode);
            Delet_queue(&pQnode);
            Delet_queue(&pQnode);
            Delet_queue(&pQnode);
            Delet_queue(&pQnode);
            Print_queue(pQnode);
            return ;
          }