下面是链表的排序,可在注释处存在疑问,请大神指教。
#include "stdio.h"#include "malloc.h"
#define LEN sizeof(struct student)
struct student
{
long num;
int score;
struct student *next;
};
struct student *create(int n)
{
struct student *head=NULL,*p1=NULL,*p2=NULL;
int i;
for(i=1;i<=n;i++)
{ p1=(struct student *)malloc(LEN);
scanf("%ld",&p1->num);
scanf("%d",&p1->score);
p1->next=NULL;
if(i==1) head=p1;
else p2->next=p1;
p2=p1;
}
return(head);
}
void print(struct student *head)
{
struct student *p;
p=head;
while(p!=NULL)
{
printf("%8ld%8d",p->num,p->score);
p=p->next;
printf("\n");
}
}
struct student *insert(struct student *head, struct student *stud)
{ struct student *p0,*p1,*p2;
p1=head; p0=stud;
if(head==NULL)
{head=p0;}
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;}
}
return(head);
}
struct student *del(struct student *head,long num)
{
struct student *p1,*p2;
p1=head;
while(p1!=NULL)
{
if(p1->num == num)
{
if(p1 == head) head=p1->next;
else p2->next=p1->next;
free(p1);
break;
}
p2=p1;
p1=p1->next;
}
return(head);
}
struct student *sort(struct student *head)
{
struct student *p1,*p2;
p2=head;p1=head;/*
p2=p2->next;为何要这三步,然而没了这三条语句,却没法交换,
可我不知道为什么要用这三条语句。为何下面循环中p1要从第二个结点开始。
p1->next=NULL;
p1=p2;*/
while(p2->next!=NULL)
{
p2=p2->next;
p1->next=NULL;
head=insert(head,p1);
p1=p2;
}
head=insert(head,p1);
return (head);
}
main()
{
struct student *head,*stu;
int n;
scanf("%d",&n);
head=create(n);
print(head);
head=sort(head);
print(head);
}