DS 双链表的实现

#include   
#include   
#include   
#include    
/*c++实现双链表的基本操作*/  
using namespace std;  
typedef struct student  
{  
        int data;  
        struct student *pre;  
        struct student *next;  
}dnode;  
//创立链表   
dnode *creat()  
{  
      dnode *head,*p,*s;  
      int x,cycle=1;  
      head=(dnode *)malloc(sizeof(dnode));  
      p=head;  
      while(cycle)  
      {  
                  cout<<"please input the data!"<>x;  
                  if(x!=0)  
                  {  
                          s=(dnode *)malloc(sizeof(dnode));  
                          s->data=x;  
                          p->next=s;  
                          s->pre=p;  
                          p=s;  
                  }  
                  else  
                  cycle=0;  
      }  
      head=head->next;  
      head->pre=NULL;  
      p->next=NULL;  
      return head;  
}  
//打印链表   
void print(dnode *head)  
{  
     dnode *p,*s;  
     p=head;  
     cout<<"正序打印双链表:"<next!=NULL)  
     {  
           cout<data<<" ";  
           p=p->next;  
     }  
     cout<data<pre!=NULL)  
     {  
            cout<data<<" ";  
            p=p->pre;  
     }                 
     cout<data<data=num;  
      while(p0->data>p1->data&&p1->next!=NULL)  
      {  
            p1=p1->next;  
      }  
      if(p0->data<=p1->data)  
      {  
             if(head==p1)  
             {  
                         p0->next=p1;  
                         p1->pre=p0;  
                         head=p0;  
             }  
             else  
             {  
                 p1->pre->next=p0;  
                 p0->next=p1;  
                 p0->pre=p1->pre;  
                 p1->pre=p0;  
             }  
      }  
      else  
      {  
          p1->next=p0;  
          p0->pre=p1;  
          p0->next=NULL;  
      }  
      return head;  
}   
//删除指定的节点  
dnode *del(dnode *head,int num)  
{  
      dnode *p1,*p2;  
      p1=head;  
      while(num!=p1->data&&p1->next!=NULL)  
       p1=p1->next;  
      if(num==p1->data)  
      {  
                      if(p1==head)  
                      {  
                                  head=head->next;  
                                  head->pre=NULL;  
                                  free(p1);  
                      }   
                      else if(p1->next==NULL)  
                      {  
                                  p1->pre->next=NULL;  
                                  free(p1);  
                      }  
                      else  
                      {  
                                  p1->next->pre=p1->pre;  
                                  p1->pre->next=p1->next;  
                                  free(p1);             
                      }  
      }  
      else  
      {  
          cout<<"没有指定的节点"<>x;  
    head=insert(head,x);  
    print(head);  
    cout<<"输入要删除的数字:"<>x;  
    head=del(head,x);  
    print(head);  
    system("PAUSE");  
    return EXIT_SUCCESS;  
}