自定义实现list及其功能

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#pragma once
#include <iostream>
#include <assert.h>
using namespace std;namespace test
{//******************************设置结点******************************template<class T>struct list_node{T _data;list_node<T>* _next;list_node<T>* _prev;list_node(const T& x = T()):_data(x),_next(nullptr),_prev(nullptr){}};//***************************************定义list迭代器***************************// typedeflist iterator<T， T&， T*>           iterator;// typedeflist iterator<T, const T&, const T*> const iterator;//list_node为结点类//template<class T>template<class T,class Ref,class Ptr>struct __list_iterator{typedef list_node<T> Node;typedef __list_iterator<T,Ref,Ptr> iterator;Node* _node;//构造函数，浅拷贝__list_iterator(Node* node): _node(node){}__list_iterator(const iterator& l):_node(l._node){}//重载!=bool operator!=(const iterator& it)const{return it._node != this->_node;}bool operator==(const iterator& s)const{return _node == s._node;}//重载 *it it.operator*()//T& operator*()//{//	return _node->_data;//}//T* operator->()//{//	return &(operator*());//&(_node->date);//}Ref operator*(){return _node->_data;}Ptr operator->(){return &(operator*());//&(_node->date);}//重载++前置iterator& operator++(){_node = _node->_next;return *this;}//重载后置++iterator operator++(int){iterator tmp(*this);_node = _node->_next;return tmp;}//重载前置--iterator& operator--(){_node = _node->_prev;return *this;}//重置后置--iterator operator--(int){iterator tmp(*this);_node = _node->_prev;return tmp;}};//**************************************模拟实现list******************************************//list_node为结点类template<class T>class list{typedef list_node<T> Node;public:typedef __list_iterator<T,T&,T*> iterator;typedef __list_iterator<T,const T&,const T*> const_iterator;const_iterator begin()const{return const_iterator(_head->_next);}const_iterator end()const{return const_iterator(_head);}iterator begin(){return iterator(_head->_next);}iterator end(){return iterator(_head);}iterator insert(iterator pos, const T& x){Node* cur = pos._node;Node* prev = cur->_prev;Node* newnode = new Node(x);prev->_next = newnode;newnode->_prev = prev;newnode->_next = cur; cur->_prev = newnode;++size;return iterator(newnode);}iterator erase(iterator pos){assert(pos != end());Node* cur = pos._node; Node* prev = cur->_prev; Node* next = cur->_next;prev->_next = next; next->_prev = prev;delete cur;size--;return iterator(next);}void push_back(const T& x){//Node* tail = _head->_prev;//Node* newnode = new Node(x);_head  tail  newnode//tail->_next = newnode;//newnode->_prev = tail;//newnode->_next = _head;//_head->_prev = newnode;insert(end(), x);}void push_front(const T& x){insert(begin(), x);}void pop_back(){erase(--end());}void pop_front(){erase(begin());}void clear(){iterator it = begin();while (it != end()){erase(it++);}size = 0;}void empty_init(){//创建并初始化哨兵位头结点_head = new Node;_head->_next = _head;_head->_prev = _head;size = 0;}void swap(list<T>& x){std::swap(_head, x._head);std::swap(size, x.size);}//构造函数list(){/*_head = new Node;_head->_next = _head;_head->_prev = _head;*/empty_init();}//模板构造函数初始化template <class InputIterator>list(InputIterator first, InputIterator last){empty_init();while (first != last){push_back(*first);++first;}}list(const list<T>& lt){empty_init();list<T> tmp(lt.begin(), lt.end());swap(tmp);}list<T>& operator=(list<T> lt){swap(lt);return *this; }size_t _size(){return size;}//析构函数~list(){clear();delete _head;_head = nullptr;}private:Node* _head;size_t size = 0;};

值得我们注意一下的是
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struct Pos{int _a1;int _a2;Pos(int a1 = 0, int a2 = 0):_a1(a1),_a2(a2){}};
void test_list2(){int x = 10;int* p1 = &x;cout << *p1 << endl;//多会用 . 多会用->Pos aa;Pos* p2 = &aa;aa._a1;p2->_a1;list<Pos> lt;lt.push_back(Pos(10, 20));lt.push_back(Pos(10, 21));list<Pos>::iterator it = lt.begin();while (it != lt.end()){//cout << (*it)._a1 << " : " << (*it)._a2 << endl;//it->是it.operator->()的类型（T*）//语法为了可读性，编译器进行了特殊处理，省略了一个->//return &(operator*());//&(_node->date);cout << it->_a1 << " : " << it->_a2 << endl;//原型cout << it->->_a1 << " : " << it->->_a2 << endl;++it;}cout << endl;}