#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("%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);
}



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->next;}
if(num==p1->num)
{if(p1==head)head=p1->next;
else p2->next=p1->next;
printf("delete:%ld\n",num);
n=n-1;
}else printf("%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);
}


void main()
{
struct student *head,stu;
long del_num;
printf("input records:\n");
head=creat();
printf("\ninput the deleted number:");
scanf("%ld",&del_num);
head=del(head,del_num);
printf((const char *)head);
printf("\ninput the insert record:");
scanf("%ld,%f",&stu.num,&stu.score);
head=insert(head,&stu);
printf((const char *) head);
}


最后main函数里的printf里面为什么要用强制类型符（const char*），如果不强制就不强制就编译不了，加了强制的时候却在运行时报错了