建立,输出,删除,插入链表的问题

如下程序时照着书上的敲进去的，虽然编译连接成功，但是运行的结果不对啊　整个过程是要建立链表，输出链表，删除结点，插入结点．　　　　　　#include<stdio.h>
#include <stdlib.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("%ld,%f",&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);
scanf("%ld,%f",&p1->num,&p1->score);
}
p2->next=NULL;
return(head);
}
void print(struct student *head)
{struct student *p;
printf("\nthese %d records are:\n",n);
p=head;
if(head!=NULL)
{do
{printf("%ld %5.1f",p->num,p->score);
p=p->next;
}while(p!=NULL);
}
}
struct student *del(struct student *head,long num)
{
struct student *p1,*p2;
if(head==NULL) printf("\nlist null!\n");return(head);
p1=head;
while(num!=p1->num&&p1->next!=NULL)
{p2=p1;p1=p1->next;}
if(num==p1->num)
{if(head==p1) head=p1->next;
else p2->next=p1->next;
printf("\ndelete %ld",num);
n=n-1;
}
else printf("\n%ld not been found!\n",num);
return(head);
}
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->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);
}
main()
{struct student *head,stu;
long del_num;
printf("input records:\n");
head=creat();
print(head);
printf("\ninput the deleted number:");
scanf("%ld",&del_num);
head=del(head,del_num);
print(head);
printf("\ninput the interted records:");
scanf("%ld,%f",&stu.num,&stu.score);
head=insert(head,&stu);
print(head);
}　　　　　　　要不你们在你们的机器上运行以下
也可能是因为我的编译环境　我的是ｖｃ＋＋６．０　 　　
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这就是谭浩强C语言书上的例11.8,11.9,11.10,11.11,还有11.7.8小节的的综合操作,我是照着书上的敲进去的,检查了好多遍,不知道哪儿有问题,求助高手!!!!!

----------------解决方案--------------------------------------------------------
建议你找个学生成绩管理系统，认真的看看建立,输出,删除,插入链表的问题你都搞明白了
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问题已经解决

----------------解决方案--------------------------------------------------------
这个程序的问题是不是　#define NULL 　0？

----------------解决方案--------------------------------------------------------
这个程序的问题是不是　#define NULL 　0？

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