C语言实现循环链表

#include<stdio.h>
#include<stdlib.h>
 
typedef struct Node
{
 int data;
 struct Node * next;
}Node, *LinkList;
 
LinkList Creat();
void Destroy(LinkList *L);
void Insert(LinkList *L, int val, int index);
void Delete(LinkList *L, int index);
void Traverse(LinkList L);
 
int main()
{
 LinkList L = Creat();
 Traverse(L);
 Insert(&L, 1, 5);
 printf("After inserting is :\n");
 Traverse(L);
 printf("After deleting is :\n");
 Delete(&L, 2);
 Traverse(L);
 Destroy(&L);
 Traverse(L);
}
 
LinkList Creat()
{
 LinkList L = (LinkList)malloc(sizeof(Node));//用L指针指向新建结点，这里L还不算尾指针
 int n;
 L->data = -1;
 L->next = L;//头结点的指针域指向头结点, 注意！这里是对尾指针的初始化。
 printf("Please enter the number you want input:(>5)");
 scanf_s("%d", &n);
 printf("input the number:\n");
 for (int i = 0; i < n; i++)
 {
 LinkList p = (LinkList)malloc(sizeof(Node));
 scanf_s("%d", &p->data);
 p->next = L->next;
 L->next = p;
 L = p;
 }
 return L;//返回尾结点的指针
}
void Destroy(LinkList *L)
{
 LinkList q = (*L)->next->next;
 LinkList p;
 (*L) = (*L)->next;
 while (q != (*L))
 {
 p = q->next;
 free(q);
 q = p;
 }
 (*L)->next = (*L);
}
void Insert(LinkList *L, int val, int index)
{
 LinkList p = (LinkList)malloc(sizeof(Node));
 p->data = val;
 LinkList q = (*L)->next;
 for (int i = 1; q != (*L) && i < index; i++)
 q = q->next;
 p->next = q->next;
 q->next = p;
 if (p == (*L))
 (*L) = p;
}
void Delete(LinkList *L, int index)
{
 LinkList q = (*L)->next, p;
 for (int i = 0; i < index; i++)
 q = q->next;
 p = q->next;
 q->next = p->next;
 free(p);
}
void Traverse(LinkList L)
{
 LinkList q = L->next->next;//这才是首元结点
 while (q != L)
 {
 printf("%d->", q->data);
 q = q->next;
 }
 printf("NULL\n");
}