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

typedef struct double_list
{
    int data;
    struct double_list *pre;
    struct double_list *next;
}List;

List *initList()
{
    List *node = (List *)malloc(sizeof(List));
    node->data = 0;
    node->pre = NULL;
    node->next = NULL;
    return node;
}

void headInsert(List *l, int data)
{
    List *node = (List *)malloc(sizeof(List));
    node->data = data;
    node->next = l->next;
    node->pre = l;
    if(l->next)
    {
        l->next->pre = node;
        l->next = node;
    }
    else
    {
        l->next = node;
    }

}

void tailInsert(List *l, int data)
{
    List *node = l;
    List *new = (List *)malloc(sizeof(List));
    new->data = data;
    while (node->next)
    {
        node = node->next;
    }
    new->next = node->next;
    node->next = new;
    new->pre = node;

}

void deleteNode(List *l, int data)
{
    List *node = l->next;
    while(node)
    {
        if(node->data == data)
        {
            node->pre->next = node->next;
            if(node->next)
            {
                node->next->pre = node->pre;
            }

            free(node);
            break;
        }
        node = node->next;
    }
}

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

int main()
{
    List *l = initList();
    headInsert(l, 0);
    headInsert(l, 1);
    headInsert(l, 2);
    headInsert(l, 3);
    tailInsert(l, 4);
    tailInsert(l, 5);
    printList(l);
    deleteNode(l, 2);
    deleteNode(l, 5);
    printList(l);
}