数据结构-双向链表

//注意双向链表中插入节点的顺序
#include<stdio.h>
#include<stdlib.h>
#include <stdbool.h>
//
  typedef struct _DNode
{
    int data;
    struct _DNode* pre; //前驱指针
    struct _DNode* next; //后继指针
}DNode, *DList;
void InitList(DList plist);
void InsertHead(DList plist, int val);
void InsertTail(DList plist, int val);
bool Delete(DList plist, int key);
DNode* Search(DList plist, int key);
int GetListLen(DList plist);
void Destroy(DList plist);
DNode* BuyNode(int val);
void ShowDList(DList plist);

//DLink.c
//#include "test.h"
int main()
{
    DNode head;
    InitList(&head);
    for (int i = 1; i < 5; ++i)
    {
        InsertHead(&head, i);
    }
    ShowDList(&head);
    printf("DList length is %d \n", GetListLen(&head));
    for (int i = 6; i < 10; ++i)
    {
        InsertTail(&head, i);
    }
    ShowDList(&head);
    printf("DList length is %d \n", GetListLen(&head));


    printf("search 第一个节点4:");
    DNode* pTmp = Search(&head, 4);
    printf("%d\n", pTmp->data);
    printf("search 最后一个节点9:");
    pTmp = Search(&head, 9);
    printf("%d\n", pTmp->data);


    printf("删除第一个节点4:\n");
    if (Delete(&head, 4))
    {
        ShowDList(&head);
    }
    else
    {
        printf("Not Fount!!!\n");
    }
    printf("删除最后一个节点9:\n");
    if (Delete(&head, 9))
    {
        ShowDList(&head);
    }
    else
    {
        printf("Not Fount!!!\n");
    }
    Destroy(&head);     //销毁链表
    return 0;
}



void InitList(DList plist)      //初始化头结点
{
    if (NULL == plist)
        return;
    plist->next = NULL;
    plist->pre = NULL;
}
DNode* BuyNode(int val)
{
    DNode* pTmp = (DNode*)malloc(sizeof(DNode));
    pTmp->data = val;
    pTmp->next = NULL;
    pTmp->pre = NULL;
    return pTmp;
}
void ShowDList(DList plist)
{
    DNode* pCur = plist->next;
    while (NULL != pCur)
    {
        printf("%5d", pCur->data);
        pCur = pCur->next;
    }
    printf("\n");
}
void InsertHead(DList plist, int val)
{
    DNode* pTmp = BuyNode(val);     //申请一个新的节点
    pTmp->next = plist->next;
    pTmp->pre = plist;
    if (NULL != pTmp->next)      //这里的判断一定不能少，读者可以试想去掉这个会发生什么
    {
        pTmp->next->pre = pTmp;       //后一个节点的前驱指向pTmp
    }
    plist->next = pTmp;
}
void InsertTail(DList plist, int val)
{
    DNode* pTmp = BuyNode(val);
    DNode* pCur = plist;
    while (NULL != pCur->next)
    {
        pCur = pCur->next;
    }
    pTmp->pre = pCur;
    pCur->next = pTmp;
}
bool Delete(DList plist, int key)
{
    DNode* pPre = plist;        //前驱结点
    DNode* pCur = plist->next;   //后继节点
    while (NULL != pCur)
    {
        if (pCur->data == key)
        {
            if (NULL != pCur->next)      //这涉及到删除最后一个节点，因为对于最后一个节点来说pCur->next为空，也即pCur->next没有pre
            {
                pCur->next->pre = pCur->pre;
            }
            pCur->pre->next = pCur->next;
            return true;
        }
        else
        {
            pPre = pCur;
            pCur = pCur->next;
        }
    }
    return false;
}
DNode* Search(DList plist, int key)
{
    DNode* pCur = plist->next;
    while (NULL != pCur)
    {
        if (pCur->data == key)
        {
            return pCur;
        }
        pCur = pCur->next;
    }
    return NULL;
}
int GetListLen(DList plist)
{
    DNode* pTmp = plist->next;
    int iCount = 0;
    while (NULL != pTmp)
    {
        ++iCount;
        pTmp = pTmp->next;
    }
    return iCount;
}
void Destroy(DList plist)
{
    DNode* pTmp = plist->next;
    while (NULL != pTmp)
    {
        plist = pTmp->next;
        free(pTmp);
        pTmp = plist;
    }
}