单链表的交换排序法

#include<stdio.h>

#include<stdlib.h>
struct link
{
    int data;
    struct link *next;
};
struct link *invent(void);
struct link *sort(struct link *head);
void outp(struct link *head);
int main()
{
    struct link *head,*p;
    printf("创建一个链表。\n");
    head=invent();
    p=head;
    outp(p);
    printf("排序后结果为：\n");
    p=sort(head);
    outp(p);
    return 0;
}
struct link *invent(void)
{
    struct link *head=NULL,*tail,*new;
    int n=0;
    while(1)
    {
        new=(struct link *)malloc(sizeof(struct link));
        printf("请输入第%d个数据，输入-1结束：",n+1);
        scanf("%d",&new->data );
        new->next =NULL;
        if(new->data==-1)
        {
            free(new);
            return  head;
        }
        else
        {
            n++;
            if(n==1)
            {
                head=tail=new;
            }
            else
            {
                tail->next =new;
                tail=new;
            }
        }
    }
}
void outp(struct link *head)
{
    while(head)
    {
        printf("%d\n",head->data );
        head=head->next ;
    }
 } 
struct link *sort(struct link *head)
{
    struct link *p,*q;
    int temp=0;
    p=head;
    while(p!=NULL)
    {
        q=p;
        temp=0;
        while(q!=NULL )
        {
            if(p->data>q->data )
            {
                temp=p->data ;
                p->data=q->data;
                q->data=temp;
            }
            q=q->next ;
        }
        p=p->next ;
    }
    return head;
 }