【C++/STL】list（常见接口、模拟实现、反向迭代器）

#pragma once 

//所以容器的反向迭代器
//迭代器适配器
namespace qjh
{
	//vector<T>::iterator
	template<class Iterator,class Ref,class Ptr>  //给谁的正向迭代器，就适配出对应的反向迭代器
	struct ReverseIterator   
	{
		typedef ReverseIterator<Iterator, Ref, Ptr> Self;

		Iterator _it;
		
		ReverseIterator(Iterator it)
			:_it(it)
		{}

		Ref operator*()
		{
			Iterator tmp = _it;  //不能修改_it，得用临时变量放回
			return *(--tmp);
		}

		Ptr operator->()
		{
			//return _it->;
			//return _it.operator->();
			return &(operator*());
		}

		Self& operator++()
		{
			--_it;
			return *this;
		}

		Self& operator--()
		{
			++_it;
			return *this;
		}

		bool operator!=(const Self& s)
		{
			return _it != s._it;
		}
	};
}

#pragma once
#include<assert.h>

#include"ReverseIterator.h"	

namespace qjh
{
	template<class T>
	struct ListNode   //需要全部被公开，用struct
	{
		ListNode<T>* _next;
		ListNode<T>* _prev;
		T _data;

		ListNode(const T& x=T())
			:_next(nullptr)
			,_prev(nullptr)
			,_data(x)
		{}
	};

	template<class T,class Ref,class Ptr>
	struct ListIterator    //对指针进行封装，因为结点的空间不是连续的
	{
		typedef ListNode<T> Node;
		typedef ListIterator<T,Ref,Ptr> Self;
		 
		Node* _node;

		ListIterator(Node* node)
			:_node(node)
		{}

		//*it
		//T& operator*()
		Ref operator*()
		{ 
			return _node->_data;
		}

		//T* operator->()
		Ptr operator->()
		{
			return	&_node->_data;
		}

		//++it
		Self& operator++()
		{
			_node = _node->_next;
			return *this;
		}

		//it++
		Self& operator++(int)
		{
			Self tmp(*this);
			_node = _node->_next;
			return tmp;
		}

		//--it
		Self& operator--()
		{
			_node = _node->_prev;
			return *this;
		}

		//it--
		Self& operator--(int)
		{
			Self tmp(*this);
			_node = _node->_prev;
			return tmp;
		}

		bool operator!=(const Self& it)
		{
			return _node != it._node;
		}

		bool operator==(const Self& it)
		{
			return _node == it._node;
		}
	};

	//template<class T>
	//struct ListConstIterator    //对指针进行封装，因为结点的空间不是连续的
	//{
	//	typedef ListNode<T> Node;
	//	typedef ListConstIterator<T> Self;

	//	Node* _node;

	//	ListConstIterator(Node* node)
	//		:_node(node)
	//	{}

	//	//*it
	//	const T& operator*()
	//	{
	//		return _node->_data;
	//	}

	//	const T* operator->()
	//	{
	//		return	&_node->_data;
	//	}

	//	//++it
	//	Self& operator++()
	//	{
	//		_node = _node->_next;
	//		return *this;
	//	}

	//	//it++
	//	Self& operator++(int)
	//	{
	//		Self tmp(*this);
	//		_node = _node->_next;
	//		return tmp;
	//	}

	//	//--it
	//	Self& operator--()
	//	{
	//		_node = _node->_prev;
	//		return *this;
	//	}

	//	//it--
	//	Self& operator--(int)
	//	{
	//		Self tmp(*this);
	//		_node = _node->_prev;
	//		return tmp;
	//	}

	//	bool operator!=(const Self& it)
	//	{
	//		return _node != it._node;
	//	}

	//	bool operator==(const Self& it)
	//	{
	//		return _node == it._node;
	//	}
	//};

	template<class T>
	class list
	{
		typedef ListNode<T> Node;
	public:
		/*typedef ListIterator<T> iterator;
		typedef ListConstIterator<T> const_iterator;*/

		typedef ListIterator<T,T&,T*> iterator;
		typedef ListIterator<T,const T&,const T*> const_iterator;

		typedef ReverseIterator<iterator, T&, T*> reverse_iterator;
		typedef ReverseIterator<const_iterator, const T&, const T*> const_reverse_iterator;


		reverse_iterator rbegin()
		{
			return reverse_iterator(end());
		}

		reverse_iterator rend()
		{
			return reverse_iterator(begin());
		}

		iterator begin()
		{
			return iterator(_head->_next);
		}

		iterator end()
		{
			return iterator(_head);
		}

		//const迭代器需要迭代器指向的内容不能修改！const iterator不是我们需要的const迭代器
		//const 迭代器本身可以++等操作
		const_iterator begin() const
		{
			return const_iterator(_head->_next);
		}

		const_iterator end() const
		{
			return const_iterator(_head);
		}

		void empty_init()
		{
			_head = new Node;
			_head->_next = _head;
			_head->_prev = _head;

			_size = 0;
		}

		list()
		{
			empty_init();
		}

		list(initializer_list<int> il)
		{
			empty_init();

			for (auto& e : il)
			{
				push_back(e);
			}
		}

		//lt2(lt1)
		list(const list<T>& lt)
		{
			empty_init();
			for (auto& e : lt)
			{
				push_back(e);
			}
		}

		void swap(list<T>& lt)
		{
			std::swap(_head, lt._head);
			std::swap(_size, lt._size);
		}

		//lt1=lt3
		list<T>& operator=(list<T> lt)
		{
			swap(lt);
			return *this;
		}

		void clear()
		{
			iterator it = begin();
			while (it != end())
			{
				it = erase(it);
			}
		}

		~list()
		{
			clear();
			delete _head;
			_head = nullptr;
		}


		//void push_back(const T& x)
		//{
		//	Node* newnode = new Node(x);
		//	Node* tail = _head->_prev;

		//	tail->_next = newnode;
		//	newnode->_prev = tail;
		//	newnode->_next = _head;
		//	_head->_prev = newnode;
		//}

		void push_back(const T& x)
		{
			insert(end(), x);
		}

		void push_front(const T& x)
		{
			insert(begin(), x);
		}

		void pop_back()
		{
			erase(--end());//迭代器不能-1，只能用-- 
		}

		void pop_front()
		{
			erase(begin());
		}

		void insert(iterator pos, const T& val)
		{
			Node* cur = pos._node;
			Node* newnode = new Node(val);
			Node* prev = cur->_prev;

			prev->_next = newnode;
			newnode->_prev = prev;
			newnode->_next = cur;
			cur->_prev = newnode;
			_size++;
		}

		iterator erase(iterator pos) //节点失效了，需要返回下一个节点
		{
			Node* cur = pos._node;
			Node* prev = cur->_prev;
			Node* next = cur->_next;

			prev->_next = next;
			next->_prev = prev;
			delete cur;
			_size--;
			return iterator(next); //匿名对象
		}

		size_t size() const
		{
			return _size;
		}

		bool empty()
		{
			return _size == 0;
		}

	private:
		Node* _head;
		size_t _size;
	};


	void test_list1()
	{
		list<int> lt;
		lt.push_back(1);
		lt.push_back(2);
		lt.push_back(3);
		lt.push_back(4);
		lt.push_back(5);

		list<int>::iterator it = lt.begin();
		while (it != lt.end())
		{
			cout << *it << " ";
			++it;
		}
		cout << endl;

		lt.push_front(10);
		lt.push_front(20);
		lt.push_front(30);

		for (auto e : lt)
		{
			cout << e << " ";
		}
		cout << endl;

		lt.pop_back();
		lt.pop_back();
		lt.pop_front();
		lt.pop_front();

		for (auto e : lt)
		{
			cout << e << " ";
		}
		cout << endl;

	}

	struct A
	{
		int _a1;
		int _a2;

		A(int a1 = 0, int a2 = 0)
			:_a1(a1)
			,_a2(a2)
		{}
	}; 

	void test_list2()
	{
		list<A> lt;
		A aa1(1, 1);
		A aa2 = { 1, 1 };

		lt.push_back(aa1);
		lt.push_back(aa2);
		lt.push_back(A(2,2));
		lt.push_back({3,3});
		lt.push_back({4,4});

		list<A>::iterator it = lt.begin();
		while (it != lt.end())
		{ 
			//cout << (*it)._a1 << ":" << (*it)._a2 << endl;
			//cout << it->_a1 << ":" << it->_a2 << endl;    //如果要遍历自定义类型，就要重载->，编译器为了可读性，省略了一个->
			cout << it.operator->()->_a1 << ":" << it.operator->()->_a2 << endl;
			++it;
		}
		cout << endl;
	}

	void PrintList(const list<int>& clt)
	{
		list<int>::const_iterator it = clt.begin();
		while (it != clt.end())
		{
			//*it += 10; 

			cout << *it << " ";
			++it;
		}
		cout << endl;
	}

	void test_list3()
	{
		list<int> lt;
		lt.push_back(1);
		lt.push_back(2);
		lt.push_back(3);
		lt.push_back(4);
		lt.push_back(5);

		PrintList(lt);

		list<int> lt1(lt);
		PrintList(lt1);

	}
}