9.10已有a,b两个链表，每个链表中的结点包括学号、成绩。要求把两个链表合并，按学号升序排列

//C程序设计第四版（谭浩强）
//章节：第九章 用户自己建立数据类型 
//题号：9.10 
//题目:已有a,b两个链表，每个链表中的结点包括学号、成绩。要求把两个链表合并，按学号升序排列
#include 
#include 
#define LEN sizeof(struct student)
struct student
{
	long num;
	float score;
	struct student *next;
};
struct student *create()	//创建链表函数 
{
	struct student *head=NULL,*p1,*p2;
	int n=0;
	p1=p2=(struct student *)malloc(LEN);
	printf("input num,score(if num=0 stop):\n");
	scanf("%ld %f",&p1->num,&p1->score);
	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)	//输出链表函数 
{
	struct student *p;
	p=head;
	printf("output list:\n");
	while(p!=NULL)
	{
		printf("%ld\t%.2f\n",p->num,p->score);
		p=p->next;
	}
	printf("\n");
}
int main()
{
	struct student *head_a,*head_b,*p1,*p2,*p3;
	long num0;
	float score0;
	printf("input list a:\n");
	head_a=create();
	printf("input list b:\n");
	head_b=create();
	p1=head_a;
	while(p1->next!=NULL)
		p1=p1->next;
	p1->next=head_b;	//连接链表a,b
	for(p1=head_a;p1->next!=NULL;p1=p1->next) 	//根据学号用选择法排序 
	{
		p3=p1;
		for(p2=p1->next;p2!=NULL;p2=p2->next)
			if(p3->num>p2->num)
				p3=p2;
		if(p1!=p3)
		{
			num0=p1->num;
			p1->num=p3->num;
			p3->num=num0;
			score0=p1->score;
			p1->score=p3->score;
			p3->score=score0;
		}
	}
	print(head_a);
	return 0;
}