#include<stdio.h>
#include<windows.h>
#include<assert.h>
typedef int DataType;

typedef struct DListNode
{
    struct DListNode* _prev;
    DataType _data;
    struct DListNode* _next;
}DListNode;

----------------------------------------------------------------

DListNode* DListInit()//链表初始化
{
    DListNode *head = (DListNode*)malloc(sizeof(DListNode));
    assert(head);
    head->_data = 0;
    head->_next = NULL;
    head->_prev = NULL;
    return head;
}

------------------------------------------------------------------

DListNode* BuyDListNode(DataType x)//建立新节点
{
    DListNode *newnode = (DListNode*)malloc(sizeof(DListNode));
    assert(newnode);
    newnode->_data = x;
    newnode->_next = NULL;
    newnode->_prev = NULL;
    return newnode;
}

--------------------------------------------------------------

void DListDestory(DListNode* head)//销毁链表
{
    assert(head);
    DListNode *flag = head;
    while (flag)
    {
        flag = flag->_next;
        free(head);
        head = flag;
    }
}

--------------------------------------------------------

void DListPrint(DListNode* head)//打印链表
{
    if (head->_next == NULL)
    {
        printf("the dlist is empty.");
        return;
    }
    head = head->_next;
    while (head)
    {
        printf("%d ", head->_data);
        head = head->_next;
    }
}

-------------------------------------------------------------

void DListPushBack(DListNode* head, DataType x)//尾插
{
    assert(head);
    DListNode *tail = head;
    while (tail->_next)
    {
        tail = tail->_next;
    }
    DListNode *newnode = BuyDListNode(x);
    assert(newnode);
    tail->_next = newnode;
    newnode->_prev = tail;

}

----------------------------------------------------------

void DListPushFront(DListNode* head, DataType x)//头插
{
    assert(head);
    DListNode *p = head->_next;
    DListNode *newnode = BuyDListNode(x);
    newnode->_next =p;
    p->_prev = newnode;
    head->_next = newnode;
    newnode->_prev = head;

}

--------------------------------------------------------

void DListPopBack(DListNode* head)//尾删
{
    assert(head);
    if ((head)->_next == NULL)
    {
        return;
    }
    DListNode *p = ((head)->_next);
    DListNode *next = p->_next;
    while (next->_next)
    {
        next = next->_next;
        p = p->_next;
    }
    p->_next = NULL;
    free(next);
}

--------------------------------------------------

void DListPopFront(DListNode* head)//头删
{
    assert(head);
    DListNode *p = head->_next;
    if (p == NULL)
    {
        return;
    }
    DListNode *next = p->_next;
    head->_next = next;
    next->_prev = head;
    free(p);

}

-----------------------------------------------------------

DListNode* DListFind(DListNode* head, DataType x)//查询
{
    assert(head);
    while (head->_next)
    {
        if ((head->_next)->_data == x)
        {
            return head->_next;
        }
        head = head->_next;
    }
    return NULL;
}

----------------------------------------------------------

void DListInsert(DListNode* pos, DataType x)//任意位置插
{
    assert(pos);
    DListNode *prev = pos->_prev;
    DListNode *newnode = BuyDListNode(x);
    newnode->_next = pos;
    pos->_prev = newnode;
    prev->_next = newnode;
    newnode->_prev = prev;

}

------------------------------------------------------

void DListErase(DListNode* pos)//任意位置删
{
    assert(pos);
    DListNode *prev = pos->_prev;
    DListNode *next = pos->_next;
    if (next == NULL)
    {
        prev->_next = NULL;
        free(pos);
        return;
    }
    prev->_next = next;
    next->_prev = prev;
    free(pos);
}