双向链表简单示例

双向链表与双向链表相比，每个元素都有两个指针分别指向前后两个元素，这意味着双向链表可以双向遍历。

简单例子如下

#include <iostream>
using namespace std;
struct Node
{
    int value;
    Node* prev;
    Node* next;
};
class List
{
    Node* head;
public:
    void initList()
    {
        head = NULL;
    }
    bool insertNode(int value, int index)
    {//第n个节点前插入,0,1,2..
        Node* newnode = new Node();
        newnode->value = value;
        if (index == 0)//插入到最前面
        {
            newnode->prev = NULL;
            newnode->next = head;
            if(head)
                head->prev = newnode;
            head = newnode;
            return true;
        }
        int count = 0;
        Node* p = head;
        while (p)
        {
            if (p->next)
            {
                count++;
                if (count == index)
                {
                    newnode->next = p->next;
                    p->next->prev = newnode;
                    p->next = newnode;
                    newnode->prev = p;
                    return true;
                }
                p = p->next;
            }
            return false;
        }
        return false;
    }
    bool deleteNode(int index)
    {//删除下标为index的元素，0，1，2..
        Node* p = head;
        while (index>0)
        {
            index--;
            if (p->next)
            {
                p = p->next;
            }
            else
                return false;
        }
        if (p->prev)
            p->prev->next = p->next;
        else
            head = p->next;
        if (p->next)
            p->next->prev = p->prev;
        return true;
    }
    void display()
    {
        Node* p = head;
        while (p)
        {
            cout << p->value << "  ";
            p = p->next;
        }
        cout << '\n';
    }
};
int main()
{
    List* list = new List();
    list->initList();
    list->insertNode(5, 0);
    list->insertNode(6, 0);
    list->insertNode(7, 0);
    list->insertNode(9, 1);
    list->display();
    list->deleteNode(2);
    list->display();
    list->deleteNode(2);
    list->display();
    return 0;
}