链表的插入程序，我这个哪里有错误啊 - -

#include
#include
#define LEN sizeof(struct student)
struct student
{
int num;
int score;
struct student *next;
};
int n=0;
struct student *creat()
{

struct student *head=NULL,*p1,*p2;
p1=p2=(struct student*)malloc(LEN);
printf("Please enter the numbers and scores of the students(enter 0 maens finishing input):\n");
scanf("%d %d",&p1->num,&p1->score);
while(p1->num!=0)
{ 
    n++;
    if(n==1)head=p1;
    else p2->next=p1;
    p2=p1;
    p1=(struct student*)malloc(LEN);
    scanf("%d %d",&p1->num,&p1->score);

}
p2->next=NULL;
free(p1);
return head;

}
struct student insert(int num,int score,struct student *p)
{

struct student *a,*t=NULL,*h=p;
a=(struct student)malloc(LEN);
a->num=num,a->score=score;

while(p->next!=NULL)
{
    if(p->num>a->num)
    {
        if(t=NULL){a->next=p,h=a;}
        else{t->next=a,a->next=p;}
        break;
    }
    t=p;
    p=p->next;
}
if(p->next=NULL){p->next=a;a->next=NULL;}
return h;

}

int main()
{
struct student *pt;
int num,score;
pt=creat();
printf("please enter a number and a score to insert into the database:\n");
scanf("%d %d",&num,&score);
pt=insert(num,score,pt);
while(pt!=NULL)
{
printf("num:%d score:%d\n",pt->num,pt->score);
pt=pt->next;
}

return 0;

}

有两个地方的==写成了=
有两处的p->next应该改成p

 #include<stdio.h>
#include<stdlib.h>
#define LEN sizeof(struct student)
struct student
{
    int num;
    int score;
    struct student *next;
};
int n=0;
struct student *creat()
{

    struct student *head=NULL,*p1,*p2;
    p1=p2=(struct student*)malloc(LEN);
    printf("Please enter the numbers and scores of the students(enter 0 maens finishing input):\n");
    scanf("%d %d",&p1->num,&p1->score);
    while(p1->num!=0)
    { 
        n++;
        if(n==1)head=p1;
        else p2->next=p1;
        p2=p1;
        p1=(struct student*)malloc(LEN);
        scanf("%d %d",&p1->num,&p1->score);

    }
    p2->next=NULL;
    free(p1);
    return head;
}
struct student *insert(int num,int score,struct student *p)
{   
    struct student *a,*t=NULL,*h=p;
    a=(struct student*)malloc(LEN);
    a->num=num,a->score=score;

    while(p!=NULL)
    {
        if(p->num>a->num)
        {
            if(t==NULL){a->next=p,h=a;}
            else{t->next=a,a->next=p;}
            break;
        }
        t=p;
        p=p->next;
    }
    if(p==NULL)
    {
        p->next=a;
        a->next=NULL;
    }
    return h;
}

int main()
{
    struct student *pt;
    int num,score;
    pt=creat();
    printf("please enter a number and a score to insert into the database:\n");
    scanf("%d %d",&num,&score);
    pt=insert(num,score,pt);
    while(pt!=NULL)
    {
        printf("num:%d score:%d\n",pt->num,pt->score);
        pt=pt->next;
    }

    return 0;
}