#include <stdio.h>
#include <math.h>
#include <string.h>
#define LEN sizeof(struct lb)
struct lb
{
    int c1;
    int c2;
    struct lb *next;
};

int n;
struct lb *tou(void)
{
    struct lb *head,*p1,*p2;
    n=0;
    p1=(struct lb*)malloc(LEN);
    p2=p1;
    scanf("%d %d",&p1->c1,&p1->c2);
    head=NULL;
    while(p1->c1!=0)
    {
        n=n+1;
        if(n==1)
        head=p1;
        else
        {
            p2=p1;
            p1=(struct lb*)malloc(LEN);
            fflush(stdin);
            scanf("%d %d",&p1->c1,&p1->c2);
            p2->next=p1;
        }
    }
    p2->next=NULL;
    return(head);
}

void main()
{
    struct lb *cr(struct lb *head);
    struct lb *sc(struct lb *head,int i);
    struct lb *p,*head;
    int i,k;
    head=tou();
    p=head;
    while(p!=NULL)
    {
        printf("%d %d\n",p->c1,p->c2);
        p=p->next;
    }
    p=head;
    printf("n=%d\n",n-1);
    printf("要删除学号请输入1\n");
    printf("要添加学号请输入2\n");
    printf("退出输入0\n");
    fflush(stdin);
    scanf("%d",&i);
    if(i==1)
    {
        printf("请输入要删除的学号：\n");
        fflush(stdin);
        scanf("%d",&k);
        head=sc(head,k);
    }
    else
        if(i==2)
        {
            head=cr(head);
        }
        else
            printf("谢谢使用\n");
    p=head;
    while(p!=NULL)
    {
        printf("%d %d\n",p->c1,p->c2);
        p=p->next;
    }

}

struct lb *sc(struct lb *head,int k)
{
    struct lb *p1,*p2;
    p1=head;
    if(head==NULL)
    {   
        printf("空表");
    }
    else
    {
        while((p1->c1!=k)&&(p1->next!=NULL))
        {
            p2=p1;
            p1=p1->next;
        }
        if(p1->c1==k)
        {
            if(p1==head)
            {
                head=p1->next;
            }
            else
            {
                p2->next=p1->next;
            }
        }
        else
            if(p1->next==NULL)
        {
            printf("找不到信息\n");
        }
    }
    return(head);
}



struct lb *cr(struct lb *head)
{
    struct lb *p0,*p1,*p2;
    p1=head;
    p2=p1;
    p0=(struct lb*)malloc(LEN);
    printf("请输入要添加的学号和成绩：\n");
    scanf("%d %d",&p0->c1,&p0->c2);
    if(head==NULL)
    {
        head=p0;
        p0->next=NULL;
    }
    else
    {
        while((p1->c1)<(p0->c1)&&(p1->next!=NULL)) /*这个地方不明白，原来是用的逻辑运算符"||"可是不行p1->c1已经大于p0->c1了 可是程序还是在自加，用&&却正常。为什么？高手能给个解释吗？*/
        {
            p2=p1;
            p1=p1->next;
        }
        if((p1->c1)>(p0->c1))
        {
            printf("c1=%d  next=%o c1=%d\n",p1->c1,p1->next,p2->c1);
            p2->next=p0;
            p0->next=p1;
            
        }
        else
            if(p1->c1==p0->c1)
            {
                printf("学号重复\n");
            }
            else
                if(p1->next==NULL)
                {
                    p1->next=p0;
                    p0->next=NULL;
                }
    }
    return(head);
}