C++ 双链表基本操作

上一篇博客主要总结了单向链表,这次再总结一下双向链表.

1.概念

  双向链表也叫双链表,是链表的一种,它的每个数据结点中都有两个指针,分别指向直接后继和直接前驱。所以,从双向链表中的任意一个结点开始,都可以很方便地访问它的前驱结点和后继结点。一般我们都构造双向循环链表。

结构图如下所示:

  《C++ 双链表基本操作》

  《C++ 双链表基本操作》

 

2.基本操作实例

 

DoubleList.cpp

#include "stdafx.h"
#include "DoubleList.h"
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
DoubleList::DoubleList()
{
        pDoubleListNode pDouList = NULL;
        // 创建双链表
        CreateDouList(pDouList);
        PrintDouList(pDouList);
        // 打印逆序链表
        PrintDouReverseList(pDouList);
        // 节点后插入节点
        InsertNodeAfter(pDouList);
        PrintDouList(pDouList);
        // 节点前插入节点
        InsertNodeBefore(pDouList);
        PrintDouList(pDouList);
        // 删除节点
        DeleteNode(pDouList);
        PrintDouList(pDouList);
        // 删除链表
        DeleteDouList(pDouList);
        PrintDouList(pDouList);
        system("PAUSE");
}
DoubleList::~DoubleList()
{
}
//创建双向链表
void DoubleList::CreateDouList(pDoubleListNode &head)
{
    char x;          // 定义成char型是用于输入'q'时可以退出,其实定义成int也能退出
    pDoubleListNode p, s;
    head = (pDoubleListNode)malloc(sizeof(DoubleListNode));
    head->next = NULL;
    head->prior = NULL;        // 构造头结点p
    p = head;
    printf("\n输入双向链表的元素,每输入一个元素后按回车,输入q表示结束.\n");
    fflush(stdin);   //清空输入缓冲区
    x = getchar();
    while (x != 'q')
    {
        s = (pDoubleListNode)malloc(sizeof(DoubleListNode));
        s->data = x - '0';  // 得到的是输入字符的ASCII码,减去30H就变成想要的数字
        s->next = NULL;
        s->prior = p;
        p->next = s;
        p = s;
        fflush(stdin);
        x = getchar();
    }
    if (x == 'q')
    {
        printf("双向链表构造完毕!\n");
    }
}
//打印双向链表
void DoubleList::PrintDouList(pDoubleListNode &head)
{
    pDoubleListNode p;
    printf("\n打印出双向链表数据为:\n");
    if (!IsDouListEmpty(head))
    {
        p = head->next;
        while (p)
        {
            printf("%d\n", p->data);
            p = p->next;
        }
    }
}
//逆序打印双向链表
void DoubleList::PrintDouReverseList(pDoubleListNode &head)
{
    pDoubleListNode p;
    printf("\n打印出逆序双向链表数据为:\n");
    if (!IsDouListEmpty(head))
    {
        p = head->next;
        while (p->next)
        {
            p = p->next;
        }
        while (p->prior)
        {
            printf("%d \n", p->data);
            p = p->prior;
        }
    }
}
//求链表长度
int DoubleList::GetDouListLength(pDoubleListNode &head)
{
    int length = 0;
    if (head == NULL)
    {
        printf("链表不存在,请先初始化!\n");
    }
    else
    {
        pDoubleListNode p = head->next;
        while (p)
        {
            length++;
            p = p->next;
        }
    }
    return length;
}
//判断链表是否为空
bool DoubleList::IsDouListEmpty(pDoubleListNode &head)
{
    if (head == NULL)
    {
        printf("链表不存在,请先初始化!\n");
        return true;
    }
    else if (head->next == NULL)
    {
        printf("链表为空!\n");
        return true;
    }
    
    return false;
}
//把双向链表置空
void DoubleList::ClearDouList(pDoubleListNode &head)
{
    if (head == NULL)
    {
        printf("链表不存在,请先初始化!\n");
    }
    else
    {
        pDoubleListNode p, q;
        p = q = head->next;   //是p、q指向第一个元素
        head->next = NULL;
        while (p)          //逐个释放元素所占内存
        {
            p = p->next;
            free(q);
            q = p;
        }
    }
}
// 删除双向链表
void DoubleList::DeleteDouList(pDoubleListNode &head)
{
    printf("\n删除双向链表\n");
    ClearDouList(head);
    free(head);
    head = NULL;
}
// 在双向链表中第i个位置后面插入元素
void DoubleList::InsertNodeAfter(pDoubleListNode &head)
{
    int  data, pos;
    pDoubleListNode p, s;
    p = head;
    int i = 0;
    printf("\n在双向链表中第i个位置后面插入元素\n");
    printf("请输入要插入的元素和位置:\n");
    scanf_s("%d%d", &data, &pos, 100);
    if (head == NULL)
    {
        printf("链表不存在,请先初始化!\n");
    }
    else if (head->next == NULL)
    {
        printf("链表为空,插入第一个元素!\n");
        s = (pDoubleListNode)malloc(sizeof(DoubleListNode));
        s->data = data;
        s->prior = NULL;    
        s->next = NULL;
        head->next = s;        // 将新结点插入head后 
    }
    else if (pos<1 || pos>GetDouListLength(head) + 1)
    {
        printf("插入位置错误!\n");
    }
    else
    {
        while (i < pos)
        {
            p = p->next;
            i++;
        }
        if (i == GetDouListLength(head))      //如果在最后一个元素后面插入data
        {
            s = (pDoubleListNode)malloc(sizeof(DoubleListNode));
            s->data = data;
            s->next = NULL;
            s->prior = p;
            p->next = s;
        }
        else
        {
            s = (pDoubleListNode)malloc(sizeof(DoubleListNode));
            s->data = data;
            s->next = p->next;
            p->next->prior = s;
            p->next = s;
            s->prior = p;
        }
    }
}
// 在双向链表中第i个位置前面插入元素
void DoubleList::InsertNodeBefore(pDoubleListNode &head)
{
    int  data, pos;
    pDoubleListNode p, s;
    p = head;
    int i = 0;
    printf("\n在双向链表中第i个位置前面插入元素\n");
    printf("请输入要插入的元素和位置:\n");
    scanf_s("%d%d", &data, &pos, 100);
    if (head == NULL)
    {
        printf("链表不存在,请先初始化!\n");
    }
    else if (head->next == NULL)
    {
        printf("链表为空,插入第一个元素!\n");
        s = (pDoubleListNode)malloc(sizeof(DoubleListNode));
        s->data = data;
        s->prior = NULL;
        s->next = NULL;
        head->next = s;        // 将新结点插入head后 
    }
    else if (pos<1 || pos>GetDouListLength(head) + 1)
    {
        printf("插入位置错误!\n");
    }
    else
    {
        while (i < pos)
        {
            p = p->next;
            i++;
        }
        if (i == 1)      // 如果在第一个元素前面插入data
        {
            s = (pDoubleListNode)malloc(sizeof(DoubleListNode));
            s->data = data;
            head->next = s;        // 将新结点插入head后 
            s->prior = head;        // 新结点的前结点指向头结点 
            s->next = p;                        // 新结点的后结点指向原head的后结点 
            p->prior = s  ;                    // 原第一个结点的前结点指向新结点 
        }
        else
        {
            s = (pDoubleListNode)malloc(sizeof(DoubleListNode));
            s->data = data;
            s->prior = p->prior;
            s->next = p;
            p->prior->next = s;
            p->prior = s;
        }
    }
}
//删除双向链表中的第i个元素
void DoubleList::DeleteNode(pDoubleListNode &head)
{
    int pos;
    int i = 0;
    pDoubleListNode p = head;
    printf("\n在双向链表中删除第i个位置的元素\n");
    printf("请输入要删除的位置:");
    scanf_s("%d", &pos, 100);
    
    if (IsDouListEmpty(head))
    {
        return;
    }
    else if (pos<1 || pos>GetDouListLength(head))
    {
        printf("删除的位置不存在!\n");
    }
    else
    {
        while (i < pos)
        {
            p = p->next;
            i++;
        }
        if (i == GetDouListLength(head))
        {
            p->prior->next = NULL;
            free(p);
        }
        else
        {
            p->prior->next = p->next;
            p->next->prior = p->prior;
            free(p);
        }
    }
}

 

DoubleList.h

#pragma once
typedef struct DoubleListNode
{
    int data;              //数据
    struct DoubleListNode *prior; //前驱
    struct DoubleListNode *next;  //后继
}DoubleListNode, *pDoubleListNode;
class DoubleList
{
public:
    DoubleList();
    ~DoubleList();
    //初始化双向链表
    void DoubleList::CreateDouList(pDoubleListNode &head);
    //打印双向链表
    void DoubleList::PrintDouList(pDoubleListNode &head);
    //逆序打印双向链表
    void DoubleList::PrintDouReverseList(pDoubleListNode &head);
    //求链表长度
    int DoubleList::GetDouListLength(pDoubleListNode &head);
    //判断链表是否为空
    bool DoubleList::IsDouListEmpty(pDoubleListNode &head);
    //把双向链表置空
    void DoubleList::ClearDouList(pDoubleListNode &head);
    //删除双向链表
    void DoubleList::DeleteDouList(pDoubleListNode &head);
    //在双向链表中第i个位置后面插入元素m
    void DoubleList::InsertNodeAfter(pDoubleListNode &head);
    // 在双向链表中第i个位置前面插入元素
    void DoubleList::InsertNodeBefore(pDoubleListNode &head);
    //删除双向链表中的第i个元素
    void DoubleList::DeleteNode(pDoubleListNode &head);
};

 

3.对链表插入节点的理解

  例如在节点i前插入一个新的节点(即上面代码中的InsertNodeBefore函数):

链表结构体为:

typedef struct DoubleListNode
{
    int data;              // 数据
    struct DoubleListNode *prior; // 前驱
    struct DoubleListNode *next;  // 后继
}DoubleListNode, *pDoubleListNode;

假设该链表由五个节点构成,分别为A,B,C,D,E

  《C++ 双链表基本操作》

 

图中假设了A,B,C,D,E的地址分别为:addressA,addressB,addressC,addressD,addressE。

下面将分析链表的前插的例子:

双链表的前插,下面这是在节点”D”前插入一个新的节点”S”的代码和分析

s = (pDoubleListNode)malloc(sizeof(DoubleListNode));  // 申请一段内存空间,指针指向首地址为addressS
s->data = data;     // 给节点S的数据赋值data
s->prior = p->prior;  // p指向D节点, p->prior表示addressC,将它赋给s->prior,则s->prior里面的值是addressC,从而指向addressC这个地址即节点C,如下图S节点的蓝线
s->next = p;       // p是addressD,将它赋给s->next,s->next中的值为addressD,也即s->next指向了D,如下图S节点的红线
p->prior->next = s;  // p->prior 是addressC,即节点C,所以p->prior->next相当于没插入S之前的addressD,插入S后,将S的首地址即addressS赋给这个位置,所以此时,由C 到D的红线断裂,这个红线目标变成了S,如下图C节点的红线
p->prior = s;     // 同理,p->prior也指向了S,即p->prior中addressC变成了addressS, D指向C的蓝线断裂。变成如下图D节点指向S节点的蓝线.

 

 《C++ 双链表基本操作》

 

     

    原文作者:sunxp
    原文地址: https://www.cnblogs.com/xiaobaiobject/p/DoubleList.html
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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