#include <stdio.h>
#include <stdlib.h>

typedef struct LNode
{
    int data;
    struct LNode *next;
}LNode;

LNode *initList()
{
    LNode *list = (LNode *)malloc(sizeof(LNode));
    if(NULL == list)
    {
        printf("malloc list node failed\n");
        return NULL;
    }
    list->data = 0;
    list->next = list;
    return list;
}

void headInsert(LNode *list, int data)
{
    LNode *node = (LNode *)malloc(sizeof(LNode));
    node->data = data;
    node->next = list->next;
    list->next = node;
    return;
}

void tailInsert(LNode *list, int data)
{
    LNode *tail = list;
    LNode *node = (LNode *)malloc(sizeof(LNode));
    node->data = data;

    while(tail->next != list)
    {
        tail = tail->next;
    }
    node->next = list;
    tail->next = node;
    return ;
}

int deleteNode(LNode *list, int data)
{
    LNode *pre = list;
    LNode *node = list->next;
    while (node != list)
    {
        if(node->data == data)
        {
            //delete data node
            pre->next = node->next;
        }
        pre = node;
        node = node->next;
    }

}

void printList(LNode *list)
{
    LNode *node = list->next;
    while (node != list)
    {
       printf("%d -> ", node->data);
       node = node->next;
    }
    printf("NULL\n");

}

int main()
{
    LNode *list = initList();
    headInsert(list, 0);
    headInsert(list, 1);
    headInsert(list, 2);
    headInsert(list, 3);
    headInsert(list, 4);
    tailInsert(list, 5);
    tailInsert(list, 6);
    printList(list);
    deleteNode(list, 2);
    deleteNode(list, 5);
    printList(list);

}