关于struct结构体的问题，程序运行到一半就卡死了

Question

#include
#include
#include

#define LEN sizeof(struct student)

struct student *creat();
struct student *del(struct student *head,int num);
void print(struct student *head);

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

int n;

void main()
{
struct student *stu, *p;
int n;

stu = creat();
p = stu;
print(p);

printf("Please enter the num you want to delete:");
scanf("%d",&n);
print( del(p,n) );

printf("\n\n");

}

struct student *creat()
{
struct student *head;
struct student *p1, *p2;

p1 = p2 = (struct student *)malloc(LEN);

printf("Please enter the num:");
scanf("%d",&p1->num);
printf("Please enter the score:");
scanf("%f",&p1->score);

head = NULL;
n = 0;

while( p1->num )
{
    n++;
    if(n==1)
    {
        head = p1;
    }
    else
    {
        p1 = p2->next;
    }
    p1 = p2;
    p1 = (struct student *)malloc(LEN);

    printf("Please enter the num:");
    scanf("%d",&p1->num);
    printf("Please enter the score:");
    scanf("%f",&p1->score);
}
return head;

}

void print(struct student *head)
{
struct student *p;
p = head;
if(head)
{
printf("There are %d records!\n",n);
do
{
printf("学号为 %d 的成绩是: %f\n",p->num,p->score);
p = p->next;
}while(p);
}
}

struct student *del(struct student *head,int num)
{
struct student *p1, *p2;

if( NULL == head )
{
    printf("This list is null!\n");
    goto END;
}

p1 = head;
while(p1->num!=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("\nDelete No: %d succeed!\n",num);
    n = n-1;
}
else
{
    printf("%d not been found!\n",num);
}

END:
return head;
}

Answer 1

while( p1->num )
这里是死循环，因为函数内没有改变num或者重新输入的逻辑