请帮忙看看关于链表的操作问题出在哪里了 这是谭浩强的C语言程序设计书上的

#include<iostream>
using namespace std;
#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 studen *)malloc(LEN);
    
    cin>>p1->num>>p1->score;
    head=NULL;
    while(p1->num!=0)
    {
        n=n+1;
        if(n==1)
            head=p1;
        else
            p2->next=p1;
        p2=p1;
        p1=(struct student*)malloc(LEN);
        cin>>p1->num>>p1->score;
        
    }
    p2->next=NULL;
    return (head);
    
}
void print(struct student *head)
{
    struct student *p;
    p=head;
    if(head!=NULL)
    do
    {
        cout<<p->num<<p->score<<endl;
        p=p->next;
    }while(p!=NULL) ;         
}
struct student *del(struct student *head,long num)
{
    struct student *p1,*p2;
    if(head==NULL)
    {
        cout<<"list is null"<<endl;
    }
    
        p1=head;
        while(num!=p1->num&&p1->next!=NULL)
        {
            p2=p1;
            p1=p1->next;
        }
        if(p1->num==num)
        {
            if(p1==head)
                head=p1->next;
            else
                p2->next=p1->next;
            n=n-1;
        }
        else
            cout<<"can't find "<<num<<endl;
        return (head);
    
}

struct student *insert(struct student *head,struct student *stud)
{
    struct student *p0,*p1,*p2;
    p0=stud;
    p1=head;
    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(p1==head)
            {
                head=p0;
            
            }
            else
            {
                p2->next=p0;
            
            }
                p0->next=p1;
        }

        
        else
        {
            p1->next=p0;
            p0->next=NULL;
        }
    }
    n=n+1;    
    return (head);
}
void main()
{
    struct student *head,stu;
    long del_num;
    cout<<"input records:"<<endl;
    head=creat();
    print(head);
    cout<<"input the deleted number:"<<endl;
    cin>>del_num;
    head=del(head,del_num);
    print(head);
    cout<<"input the inserted record:"<<endl;
    cin>>stu.num>>stu.score;
    head=insert(head,&stu);
    print(head);
}