数据结构-4-双链表

在单链表的实现中，我们可以清晰感觉到，要访问链表的尾时必须要遍历链表，这样效率就打了折扣，为了解决这一矛盾，就诞生了双链表。

双链表：每一个节点不仅拥有存储数据的数据变量和指向数据的下一个变量的下一个指针变量，而且含有指向数据变量的前一个变量的一个先前指针变量。

这里写图片描述


#include<stdio.h>
#include<assert.h>
#include<Windows.h>

typedef int DataType;

typedef struct DlistNode
{
    struct DlistNode* next;
    struct DlistNode* prev;
    DataType data;
}DlistNode;


DlistNode* BuyDlistNode(DataType x);
DlistNode* DListInit();
void DListDestory(DlistNode* head);
void DListPrint(DlistNode* head);

void DListPushBack(DlistNode* head, DataType x);
void DListPushFront(DlistNode* head, DataType x);
void DListPopBack(DlistNode* head);
void DListPopFront(DlistNode* head);

DlistNode* DListFind(DlistNode* head, DataType x);
void DListInsert(DlistNode* pos, DataType x);
void DListErase(DlistNode* pos);

void DListPrint(DlistNode* head);
DlistNode* DListInit();

void test1();
void test2();

DlistNode* BuyDlistNode(DataType x)
{
    DlistNode*new = (DlistNode*)malloc(sizeof(DlistNode));
    assert(new);

    new->data = x;
    new->next = NULL;
    new->prev = NULL;
    return new;
}
DlistNode* DListInit()
{
    DataType x = 10;
    DlistNode*list = BuyDlistNode(x);

    list->next = list;
    list->prev = list;

    return list;
}
void DListDestory(DlistNode*head)
{
    DlistNode*cur = head->next;
    while (cur!=head)
    {
        DlistNode*next = cur->next;
        free(cur);
        cur = next;
    }
    free(head);
    head = NULL;
}
void DListPrint(DlistNode* head)
{
    DlistNode*cur = head->next;
    while (cur != head)
    {
        printf("%d ", cur->data);
        cur = cur->next;
    }
    printf("head\n");
}

void DListPushBack(DlistNode* head, DataType x)
{
    /*assert(head);
    DlistNode*tail = head->prev;
    DlistNode* newnode = BuyDlistNode(x);
    tail->next = newnode;
    newnode->prev = tail;

    newnode->next = head;
    head->prev = newnode;*/
    DListInsert(head->prev, x);
}

void DListPopBack(DlistNode* head)
{
    /*assert(head);
    DlistNode*tail = head->prev;
    DlistNode*prev = tail->prev;
    if (head->next == NULL)
        return;

    free(tail);
    tail = NULL;

    prev->next = head;
    head->prev = prev;*/
    DListErase(head->prev);
}

void DListPushFront(DlistNode* head, DataType x)
{
    /*assert(head);
    DlistNode*next = head->next;
    DlistNode*newnode = BuyDlistNode(x);

    head->next = newnode;
    newnode->prev = head;

    newnode->next = next;
    next->prev = newnode;*/
    DListInsert(head, x);
}

void DListPopFront(DlistNode* head)
{
    /*assert(head);
    DlistNode*next = head->next;
    DlistNode*newnext = next->next;
    free(next);
    next = NULL;

    head->next = newnext;
    newnext->prev = head;*/

    DListErase(head->next);
}

DlistNode* DListFind(DlistNode* head, DataType x)
{
    assert(head);
    DlistNode*cur = head->next;
    if (x == cur->data)
        return cur;
    while (cur != head)
    {
        if (x == cur->data)
            return cur;
        cur = cur->next;
    }
    return NULL;
}

void DListInsert(DlistNode* pos, DataType x)
{
    DlistNode*newnode = BuyDlistNode(x);
    DlistNode*next = pos->next;
    //pos newnode next
    pos->next = newnode;
    newnode->prev = pos;

    newnode->next = next;
    next->prev = newnode;
}
void DListErase(DlistNode* pos)
{
    DlistNode*prev = pos->prev;
    DlistNode*next = pos->next;
    free(pos);
    pos = NULL;
    prev->next = next;
    next->prev = prev;
}

void test1()
{
    DlistNode* list = DListInit();
    DListPushBack(list, 1);
    DListPushBack(list, 2);
    DListPushBack(list, 3);
    DListPushBack(list, 4);
    DListPushBack(list, 5);
    DListPrint(list);

    DListPopBack(list);
    DListPopBack(list);
    DListPrint(list);
}

void test2()
{
    DlistNode* list = DListInit();
    DListPushFront(list, 1);
    DListPushFront(list, 2);
    DListPushFront(list, 3);
    DListPushFront(list, 4);
    DListPushFront(list, 5);
    DListPrint(list);
    printf("%d\n", DListFind(list, 3)->data);

    DListPopFront(list);
    DListPopFront(list);
    DListPrint(list);
}

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#include"fun.h"

int main()
{
    test2();
    system("pause");
    return 0;
}

数据结构-4-双链表

数据结构-4-双链表

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