c++STL list 简单模拟实现

分享一份c++stl库list简单模拟实现。

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​
#pragma once
#include<assert.h>

namespace my_list {
	template<class T>
	class ListNode {
		typedef ListNode<T> Node;
	public:
		//list中需要访问node中的元素，所以用公有
		Node* _prev;
		Node* _next;
		T _val;
		//初始化
		ListNode(const T& val = T())
			:_val( val),
			_prev(nullptr),
			_next(nullptr)
		{}
	};
	//ref是t的引用，Ptr是t的指针
	template<class T,class Ref ,class Ptr>
	class ListIterator {
		typedef ListNode<T> Node;
		typedef ListIterator<T,Ref,Ptr> iterator;
	public:
		Node* _Node;
		ListIterator(Node* node)
			:_Node(node)
		{}
		Ref operator*() 
		{
			return _Node->_val;
		}
		Ptr operator->()
		{
			return &_Node->_val;
		}
		//++it
		iterator& operator++() {
			_Node = _Node->_next;
			return *this;
		}
		//it++
		iterator operator++(int) {
			iterator tmp(*this);
			_Node = _Node->_next;
			return tmp;
		}//--it
		iterator& operator--() {
			_Node = _Node->_prev;
			return *this;
		}
		//it++
		iterator operator--(int) {
			iterator tmp(*this);
			_Node = _Node->_prev;
			return tmp;
		}
		bool operator!=(const iterator& it) {
			return it._Node != _Node;
		}
		bool operator==(const iterator& it) {
			return it._Node == _Node;
		}
	};
	template<class T>
	class List {
		typedef ListNode<T> Node;
		Node* _head;
		size_t _size;
	public:
		typedef List<T> list;
		typedef ListIterator<T, T&, T*> iterator;
		typedef ListIterator<T ,const T& ,const T*> const_iterator;
		void Init()
		{
			_head = new Node;
			_head->_next = _head;
			_head->_prev = _head;

			_size = 0;
		}
		List()
		{
			Init();
		}
		List(const List<T>& it) {
			Init();
			for (auto e : it)
			{
				push_back(e);
			}
		}
		list& operator=(list A) {
			swap(A);
			return *this;
		}
		iterator begin() {
			return _head->_next;
		}
		iterator end() {
			return _head;
		}
		const_iterator begin()	const {
			return _head->_next;
		}
		const_iterator end()	const {
			return _head;
		}
		void insert(iterator it, T val) {
			Node* tmp = new Node(val);
			Node* prev = it._Node->_prev;
			Node* next = it._Node;
			prev->_next = tmp, tmp->_prev = prev;
			next->_prev = tmp, tmp->_next = next;
			_size++;
		}
		void push_back(T val)
		{
			insert(end(), val);
		}
		void push_front(T val)
		{
			insert(begin(), val);
		}
		iterator earse(iterator it)
		{
			Node* node = it._Node;
			Node* prev = node->_prev;
			Node* next = node->_next;
		
			delete node;
			prev->_next = next;
			next->_prev = prev;
			_size--;
			return next;
		}
		void pop_back() {
			earse(begin());
		}
		void pop_front() {
			earse(--end());
		}
		void swap(list A)
		{
			std::swap(_head, A._head);
			std::swap(_size, A._size);
		}
		size_t size() {
			return _size;
		}
		void clear() {
			iterator it = begin();
			while (it != end())
			{
				it = earse(it);
			}
		}
		~List() {
			clear();
			delete _head;
			_head = nullptr;
		}
	};


​