请高帮帮忙,这个程序错在那?
怎样修正????








#include<stdio.h>
#include<malloc.h>

#define NULL 0
#define LEN sizeof(struct student)

struct student
{long num;
float score;
struct student *next;
};
int n;

struct student *creat(void)
{
struct student *head;
struct student *p1,*p2;
n=0;
p1=p2=(struct student*)malloc(LEN);
scanf("%d,%f",&p1->num,&p1->score);
head=NULL;
while(p1->num!=0){
n++;
if(n==1) head=p1;

else p2->next=p1;
p2=p1;
p1=(struct student*)malloc(LEN);
}
p2->next=NULL;
return(head);
}

struct student * insert(struct student *head,struct student *stu)
{
struct student *p0,*p1,*p2;
p1=head;
p0=stu;
if(head==NULL)
{
head=p0;p0->next=NULL;
}
else
{while((p0->num>p1->num )&&(p1->next!=NULL))
{
p2=p1;
p1=p1->next;
}
if(p0->num<=p1->num)
{if(head==p1) head=p0;
else
p2->next=p0;
p0->next=p1;
}
else
{
p1->next=p0;
p0->next=NULL;
}
}
n=n+1;
return(head);
}

struct student *del(struct student *head,long num)
{
struct student *p1,*p2;
if(head==NULL){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:%d\n",num);
free(p1);
n=n-1;
}
else
printf("\n%d not been found! ",num);
end;
return(head);
}

void print(struct student *head)
{
struct student *p;
printf("\n Now,These %d records are:\n",n);
p=head;
if(head!=NULL)
{
do
{
printf("%ld,%2f\n",p->num,p->score);
p=p->next;
}while(p!=NULL);
}
}
void main()
{
struct student *head,*stu;
long del_num;
int x;
printf("\n请选择所要进行的操作:\n");
printf(" 1.初始化链式线型表(以输入0结束)\n");
printf(" 2.插入新的元素\n");
printf(" 3.删除所选的元素\n");
printf(" 4.输出表中的现有元素\n");
scanf("%d",&x);
printf("\n");
switch(x)
{
case '1': printf("input recrds:\n");
head=creat();break;

case '2': printf("\n input the inserted record:");
stu=(struct student *)malloc(LEN);
scanf("%ld,%f",&stu->num,&stu->score);
while(stu->num!=0)
{
head=insert(head,stu);
printf("\n input the inserted record:");
stu=(struct student *)malloc(LEN);
scanf("%ld,%f",&stu->num,&stu->score);
}
break;

case '3': printf("\n input del_num:");
scanf("%ld",&del_num);
while(del_num!=0)
{
head=del(head,del_num);
printf("\n input del_num:");
scanf("%ld",&del_num);
}
break;

case '4': printf("\n The now list are:");
print(head);
break;

default: printf("\nERROR");
}
}