#include<stdio.h>
#include<stdlib.h>
#define TRUE 1
#define FASLE 0//定义宏标识判断是否成功
typedef struct Node {
       int data;
       struct Node* next;
}Node;
 Node* InitList() {
        Node* list = (Node*)malloc(sizeof(Node));
        list->data = 0;//创建节点保存data
        list->next = list;
        return list;
}
 void headInsert(Node*list,int data) {
        Node* node = (Node*)malloc(sizeof(Node));
        node->data = data;
        node->next = list->next;
        list->next = node;
        list->data++;//记录节点数
 }
 
void tailInsert(Node* list,int data) {//带入头指针
       Node* n = list;//保存list头节点，用n这个指针变量移动进行判断方便判断
       Node* node = (Node*)malloc(sizeof(Node));
       node->data = data;
       while (n->next != list) {
               n = n->next;
       }
       node->next = list;
       n->next = node;
       list->data++;
 }
 void printList(Node* list) {//传入头结点
        Node* node =list->next;//拿到第一个节点赋值给node
        while (node != list) {//尾节点不等于头结点
                printf("%d->", node->data);
                node = node->next;
        }
        printf("NULL\n" );
               
 }
 int num(Node* list) {
        return list->data;
 }
 
 int DeleteList(Node* list,int data) {
        Node* prenode = list;
        Node* current = list->next;//设置一个指向头街点的node节点
        while (current!=list) {
                if (current->data == data) {
                       prenode->next = current->next;
                       free(current);
                       list->data--;
                       return TRUE;
                }
                else {
                       prenode = current;
                       current = current ->next;
                }
        }
        return FASLE;
 }
int main() {
       Node* list=InitList();
       headInsert(list, 1);
       headInsert(list, 2);
       headInsert(list, 3);
       headInsert(list, 4);
       tailInsert(list, 5);
       tailInsert(list, 6);
       tailInsert(list, 43);
       tailInsert(list, 21);
       tailInsert(list, 31);
       printList(list);
       printf("%d\n", num(list));
       DeleteList(list, 4);//删除元素为4的节点
       printList(list);
       printf("%d\n", num(list));
       DeleteList(list, 31);//删除元素为4的节点
       printList(list);
       printf("%d\n", num(list));
       return 0;
}