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

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

LNode *initList()
{
    LNode *list = (LNode *)malloc(sizeof(LNode));
    if(list == NULL)
    {
        return NULL;
    }
    list->data = 0;
    list->next = NULL;
    return list;
}

int headInsert(LNode *list, int data)
{
    LNode *node = (LNode *)malloc(sizeof(LNode));
    if(NULL == node)
    {
        printf("malloc new node failed\n");
        return -1;
    }
    node->data = data;
    node->next = list->next;
    list->next = node;
    return 0;
}

int tailInsert(LNode *list, int data)
{
    // LNode *head = list;
    LNode *node = (LNode *)malloc(sizeof(LNode));
    if(NULL == node)
    {
        printf("malloc new node failed\n");
        return -1;
    }
    node->data = data;
    node->next = NULL;
    list = list->next;
    while (list->next)
    {
        list = list->next;
    }
    list->next = node;
    return 0;
}

int deleteNode(LNode *list, int data)
{
    LNode *pre = list;
    LNode *cur = list->next;
    while(cur)
    {
        if(cur->data == data)
        {
            pre->next = cur->next;
            free(cur);
            break;
        }
        else
        {
            pre = cur;
            cur = cur->next;
        }
    }
    return 0;
}

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

int main()
{
    LNode *list = initList();
    if(NULL == list)
    {
        printf("init failed\n");
        return 0;
    }
    headInsert(list, 0);
    headInsert(list, 1);
    headInsert(list, 2);
    headInsert(list, 3);
    tailInsert(list, 4);
    tailInsert(list, 5);
    tailInsert(list, 6);
    tailInsert(list, 7);
    printList(list);
    deleteNode(list, 2);
    deleteNode(list, 6);
    printList(list);
    return 0;
}