链表的基本操作

　　链表可以进行创建、插入、删除、查找、改变等操作，不过这个程序存在一个很大的问题——就是在插入的时候不可以第二次插入，如果有谁能帮我完善一下那就再好不过了。有缺陷的涵数是struct student *insert(struct student *head, struct student *stud)

/*win-tc*/
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
#define Esc 27 /*定义键盘退出键Esc*/
#include"ctype.h"
#define NULL 0
#define LEN sizeof(struct student)
struct student
{ long num;
float score;
struct student *next;
};
int n;

/*创建链表*/
struct student *creat()
{
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);
}

/*打印链表*/
void print(struct student *head)
{
struct student *p;
printf("/nNow,These %d records are:/n",n);
p=head;
if(head!=NULL)
do
{
printf("%ld %5.1f/n",p->num,p->score);
p=p->next;
}while(p!=NULL);
printf("/npress a key to continue.");
getch();
}

/*删除链表元素*/
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(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);
}

/*插入链表元素*/
/*这个涵数存在一个问题，就是不能第二次插入成绩*/
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);
}

/*查找链表元素*/
struct student *find(struct student *head, long num)
{
struct student *p1,*p2;

p1=head;

if(head==NULL)
{
printf("/nlist null!/n");
return(head);
}
else
{
while(num!=p1->num && p1->next!=NULL)
{
p2=p1;
p1=p1->next;
}
if(num==p1->num)
{
printf("have fond the number is:/n%ld %5.1f/n",p1->num,p1->score);
return(head);
}
else
{
printf("the find number is not in the list!/n");
return(head);
}
}
}

/*改变链表元素的成绩*/
struct student *change(struct student *head, long num)
{
struct student *p1,*p2;
struct student stu;
if(head==NULL)
{
printf("/nlist null!/n");
return(head);
}
else
{
while(num!=p1->num && p1->next!=NULL)
{
p2=p1;
p1=p1->next;
}
if(num==p1->num)
{
printf("the before score is:%5.1f/n",p1->score);
printf("please input the change score!/n");
scanf ("%f",&stu.score) ;
p1->score=stu.score ;
return(head);
}
else
{
printf("the find number is not in the list!/n");
return(head);
}
}
}

/*主涵数*/
void main()
{
struct student *head,stu;
long del_num;
long find_num;
long change_num;
char ckey='a';
int istate=0;
do
{
clrscr();
printf("1:intput records:/n");
printf ("2:intput the deleted number:/n");
printf ("3:intput the inserted number:/n");
printf("4:please input the finding number:/n");
printf("5:please input the change number:/n");
printf("6:output records:/n");
printf("Esc:exit/n");
printf("please input your choose(1-4)/n/n");
ckey=getch();
if(ckey=='1') /*创建*/
{
printf("please input records(num,score),by the end of 0:/n/n");
head=creat();
print(head);
istate=1;
}
else if((istate==0)&&(ckey!=Esc))
{
printf("/nERROR:you must input records first!");
printf("/npress a key to continue.");
getch();
}
else if(ckey=='2') /*删除*/
{
printf ("/nplease intput the deleted number:/n/n");
scanf ("%ld",&del_num);
head=del(head,del_num);
print(head);
}
else if(ckey=='3') /*插入*/
{
printf (" /nplease intput the inserted number(num,score):/n/n");
scanf ("%ld,%f",&stu.num,&stu.score) ;
head=insert(head,&stu);
print(head);
}
else if(ckey=='4') /*查找*/
{
printf(" /nplease input the finding number:/n/n");
scanf ("%ld,",&find_num) ;
head=find(head,find_num);
print(head);
}
else if(ckey=='5') /*改变*/
{
printf(" /nplease input the change number:/n/n");
scanf ("%ld,",&change_num) ;
head=change(head,change_num);
print(head);
}
else if(ckey=='6') /*打印*/
{
print(head);
}
}
while(ckey!=Esc); /*按键盘上的Esc键退出*/
}