//实现双向链表
#pragma once
#include<iostream>
#include<string>
#include<vector>
using namespace std;class Iterator;
class ForwardIterator;
class ReverseIterator;//链表的最小组成部分是一个节点，先实现一个节点
struct Node //c++中struct和class没有区别，只不过class默认是private，struct默认是public
{Node(int n) :name(n) {} //构造函数int name; //数据Node* next = nullptr; //后继Node* prev = nullptr; //前驱
};//定义双向链表
class MyList
{
public://定义成内联函数（内存替换，不能太复杂，空间换时间），获取链表节点个数inline int getCount(){return m_count;}//获取链表头节点inline Node* head(){return m_head;}//获取链表尾节点inline Node* tail(){return m_tail;}//定义插入节点的操作,头部插入，中间插入，尾部插入Node* insert(Node* node,int name);Node* pushFront(int name);Node* pushBack(int name);Iterator* getIterator(bool isReverse);private:Node* m_head = nullptr; //定义一个指向头结点的指针Node* m_tail = nullptr;  //定义一个指向尾结点的指针int m_count = 0;
};
Node* MyList::insert(Node* node, int name)
{Node* newNode = nullptr;//node是链表中的哪个节点，如果是头结点if (node == m_head){newNode = pushFront(name);}else if (node == m_tail){newNode = pushBack(name);}else{newNode = new Node(name);newNode->next = node;newNode->prev = node->prev;node->prev->next = newNode;node->prev = newNode;m_count++;}return newNode;
}Node* MyList::pushFront(int name)
{Node* newNode = new Node(name);if (m_count == 0){m_head = m_tail = newNode;}else{newNode->next = m_head;m_head->prev = newNode;m_head = newNode;}m_count++;return newNode;
}Node* MyList::pushBack(int  name)
{Node* newNode = new Node(name);if (m_count == 0){m_head = m_tail = newNode;}else{newNode->prev = m_tail;m_tail->next = newNode;m_tail = newNode;}m_count++;return newNode;
}//定义抽象的迭代器类
class Iterator
{
public:Iterator(MyList* list) : m_list(list) {} //构造函数，保存好要遍历的链表Node* current(){return m_current;}virtual Node* first() = 0;virtual Node* next() = 0;virtual bool isDone() = 0;protected:MyList* m_list = nullptr;Node* m_current = nullptr;
};//定义一个正向遍历的链表
class ForwardIterator:public Iterator
{
public:using Iterator::Iterator;Node* first() override{m_current = m_list->head();return m_current;}Node* next() override{m_current = m_current->next;return m_current;}bool isDone() override{return m_current == nullptr;}
};
//定义一个反向遍历的链表
class ReverseIterator :public Iterator
{
public:using Iterator::Iterator;Node* first() override{m_current = m_list->tail();return m_current;}Node* next() override{m_current = m_current->prev;return m_current;}bool isDone() override{return m_current == nullptr;}
};Iterator* MyList::getIterator(bool isReverse)
{Iterator* it = nullptr;if (isReverse){it = new ReverseIterator(this);}else{it = new ForwardIterator(this);}return it;
}
int main()
{vector<int> nameList = {0,1,2,3,4,5,6,7,8,9};MyList ls;for (auto& itr : nameList){ls.pushBack(itr);}//正向遍历Iterator* it = ls.getIterator(true);for (auto begin = it->first(); !it->isDone(); it->next()){cout << it->current()->name << endl;}cout << "==================================================" << endl;Iterator* ir = ls.getIterator(false);for (auto begin = ir->first(); !ir->isDone(); ir->next()){cout << ir->current()->name << endl;}return 0;
}