2.将基本链表改为循环链表

没什么大的变动，所以书中这部分只用了两段话略过

#include<stdio.h>
#include<stdlib.h>
typedef int ElemType;
struct Node{
    Node *next;
    ElemType data;
};
void CreateList(Node*&L)
{
    L = (Node*)malloc(sizeof(Node));
    if(!L) exit(-2);
    L->next = L;
    L->data = 0;
}
void InsertList(Node*&L,ElemType e)
{
    Node *p = L;
    for(int i=0;i<L->data;++i)
    {
        p=p->next;
    }
    Node *s = NULL;
    s=(Node*)malloc(sizeof(Node));
    s->data = e;
    s->next = p->next;
    p->next = s;
    ++(L->data);
}
void DeleteList(Node*&L,int n)
{
    Node*p = L;
    if(n<1||n>L->data) exit(-2);
    for(int i = 0;i<n-1;i++)
    {
        p=p->next;
    }
    Node*temp = p->next;
    p->next = p->next->next;
    free(temp);
    --L->data;
}
void ShowList(Node*&L)
{
    Node *p = L;
    while(p->next!=L){
        printf(">%d\t",(p)->data);
        p=p->next;
    }

    printf("\n");
}
int main()
{
    Node *N1;
    CreateList(N1);
    InsertList(N1,1);
    ShowList(N1);
    InsertList(N1,2);
    ShowList(N1);
    InsertList(N1,3);
    ShowList(N1);
    InsertList(N1,4);
    ShowList(N1);
    InsertList(N1,5);
    ShowList(N1);
    DeleteList(N1,1);
    ShowList(N1);
    DeleteList(N1,2);
    ShowList(N1);
}