データ構造の---c言語による双方向リンク操作の実現

#include<stdio.h>   
#include<stdlib.h>   
typedef int ElemType;
typedef struct DoubleLinkedList  
{  
     ElemType data;  
     struct DoubleLinkedList *pre;  
     struct DoubleLinkedList *next;  
}DlinkedList_Node;  
   
//       
DlinkedList_Node* create_dlink()  
{  
   DlinkedList_Node *head,*p,*s;  
   int x;  
   head = (DlinkedList_Node*)malloc(sizeof(DlinkedList_Node));  
   p = head;  
   while(1)  
   {  
       printf("         ，  0    :
");  
       scanf("%d",&x);
       if(x != 0)  
       {  
          s = (DlinkedList_Node*)malloc(sizeof(DlinkedList_Node));  
          s ->data = x;  
          s-> pre = p;  
          p->next = s;  
          p=s;  
       }  
       else  
       {  
          printf("
      
");  
          break;  
       }  
    }  
    p->next = NULL;  
    head = head ->next;  
    head->pre = NULL;  
    return head;  
}  
    
//  、         
void print_dlink(DlinkedList_Node *head)  
{ 
	DlinkedList_Node *p,*s;  
    p = head;  
    printf("            ：
");  
    while(p)  
    {  
        printf("%d ",p->data);  
        s = p;  
        p = p->next;  
    }  
    printf("
             : 
");  
    while(s)  
    {  
        printf("%d ",s->data);  
        s = s->pre;  
    }  
    printf("
 
");  
}  
    
//              
DlinkedList_Node* delete_dlinkedlist_node(DlinkedList_Node *head,int i)  
{  
    DlinkedList_Node *p;  
    p = head;  
    if(p->data == i)  
    {  
        head = p->next;  
        head->pre = NULL;  
        free(p);  
        return head;  
    }  
    while(p)  
    {  
        if(p->data == i)  
        {  
         	p->pre->next = p->next;  
            p->next->pre = p->pre;  
            free(p);  
            return head;  
         }  
         p = p->next;  
     }  
     printf("        ！，           
");  
     return head;  
 }

//         
DlinkedList_Node* insert_dlinkedlist_node(DlinkedList_Node *head,int i)  
{  
   
   DlinkedList_Node *p,*temp;  
   p = head;  
   temp = (DlinkedList_Node*)malloc(sizeof(DlinkedList_Node));  
   temp ->data = i;  
   if(i < p->data)//       ，          
   {  
       head = temp;  
       head->next = p;//  p    head   
       head->pre = NULL;  
       p->pre = head;//  p    head   
       return head;  
    }

    while(p != NULL && i > p->data)//            
    {  
       p = p->next;  
    }  
    if(i < p->data)//                  
    {  
        temp ->next = p;  
        temp ->pre = p->pre;  
        p ->pre->next = temp;  
        p ->pre = temp;  
        return head;  
     }      
	else//         ，               
     {  
         p->next = temp;  //       ，p==NULL   
         temp ->pre = p;  
         temp ->next = NULL;  
         return head;  
      }  
}  
    
int main()  
{  
    DlinkedList_Node *head;  
    head = create_dlink();  
    print_dlink(head);  
    return 0;
}