c语言||链表:请问下面的代码哪里错了？？

#include <stdio.h>
#include <stdlib.h>
struct Node

{

   int num;

   struct Node *next;

};

int main(void)

{

   struct Node *head,*tail, *p;

   int num;

   int size = sizeof(struct Node);

   head=tail=NULL;

   printf("请输入编号:\n");

   scanf("%d", &num);

   /*建立单向链表*/

   while(num != 0)

   {

     p = (struct Node *) malloc(size);

     p->num = num;

     p->next=NULL;

     tail->next=p;
     tail=p;

     scanf("%d", &num);

   }

   /*输出单向链表*/

   printf("The single linked list is:\n");

   for(p=head; p->next!=NULL; p=p->next)

        printf("%d\n", p->num);

  return 0;

}

原题

下面程序功能如下：输入若干个整数编号，输入编号为0时结束，用单向链表组织这些编号信息后，再按顺序输出。

	
#include <stdio.h>
#include <stdlib.h>
struct Node
 
{
 
   int num;
 
   struct Node *next;
 
};
 
int main(void)
 
{
 
   struct Node *head,*tail, *p;
 
   int num;
 
   int size = sizeof(struct Node);
 
   head=tail=NULL;
 
   printf("请输入编号:\n");
 
   scanf("%d", &num);
 
   /*建立单向链表*/
 
   while(num != 0)
 
   {
 
     p = (struct Node *) malloc(size);
 
     p->num = num;
 
     p->next=NULL;
 
     tail->next=p;
     tail=p;
 
     scanf("%d", &num);
 
   }
 
   /*输出单向链表*/
 
   printf("The single linked list is:\n");
 
   for(p=head; p->next!=NULL; p=p->next)
 
        printf("%d\n", p->num);
 
  return 0;
 
}

1. 请用代码插件来显示代码。

好像你的head没赋值呀