刚起步学C/C++求大神指导下，这段程序问题出在哪里，谢谢。

#include <stdio.h>
#include <stdlib.h>
#define LEN sizeof(struct student) struct student
{
long num;
float score;
struct student * next;
}liststudent,*lis;
int n;
/*建立链表*/
struct student * create()
{struct student * head, *p1, *p2;
n=0;head=NULL;
p1=p2=(struct student *)malloc(LEN);
scanf("%ld,%f",&p1->num,&p1->score);p1->next=NULL;
while(p1->num!=0)
{++n;
if(n==1)head=p1;
else p2->next=p1;
p2=p1;
p1=(struct student *)malloc(LEN);
scanf("%ld,%f",&p1->num,&p1->score);
p1->next=NULL;
}
free(p1);
return(head);
}
/*插入节点*/
struct student * insert(struct student * head,struct student * stud)
{
struct student *p0,*p1,*p2;
p1=head;
p0=stud;
if(head==NULL)
{head=p0;p0->next=NULL;}
else
{
while((p0->num>p1->num)&&(p1!=NULL))
{p2=p1;p1=p1->next;}
if(head==p1)
{p0->next=head;
head=p0;
}
else
{p2->next=p0;
p0->next=p1;
}
}
++n;
return(head);
}
/*删除节点*/
struct student *delete(struct student * head,long num)
{
struct student *p1,*p2;
if(head==NULL)
{
printf("\nlist null!\n");goto end;
}
p1=head;
while(num!=p1->num && p1->next!=NULL)
{p2=p1;p1=p1->next;}
if(num==p1->num)
{if(p1==head)
head=p1->next;
else
p2->next=p1->next;
printf("delete:%ld\n",num);
free(p1);
n--;
}
else
printf("%ld not been found!\n",num);
end:return(head);
}
/*链表输出*/
void print(struct student * head)
{struct student *p;
printf("\nNow,These %d nodes are:\n",n);
p=head;
if(head!=NULL)
do
{
printf("%ld %5.1f\n",p->num,p->score);
p=p->next;
}while(p!=NULL);
}
/*查找节点*/
struct student * find(struct student * head,long num)
{
struct student *p1,*p2;
if(head==NULL)
{printf("\n list null!\n");goto end;}
p1=head;
while(num!=p1->num && p1!=NULL)
{p2=p1;p1=p1->next;}
if(p1!=NULL)
printf("find: %ld %5.2f\n",num,p1->score);
else
printf("%ld not been found!\n",num);
end:
return(head);
}
/*主函数*/
void main()
{
long checknum=5;
*lis=* create();
print(lis);
* find(lis,checknum); }