[C++]list及其模拟实现

目录

C++：list及其模拟实现

                        成员函数接口总览

                        结点类的模拟实现

                                构造函数

                        迭代器类的模拟实现

                                构造函数

                                ++运算符的重载

                                --运算符的重载

                                ==运算符的重载

                                !=运算符的重载

                               *运算符的重载

                                ->运算符的重载

                        list的模拟实现

                                默认成员函数

                                构造函数

                                拷贝构造函数

                                赋值运算符重载

                                析构函数

                                迭代器相关函数

                                        begin和end

                                访问容器相关函数

                                        front和back

                                插入、删除函数

                                        insert

                                        erase

                                        push_back和pop_back

                                        push_front和pop_front

                                其他函数

                                        size

                ​​​​​​​                        resize

                ​​​​​​​                        clear

                ​​​​​​​                        empty

                ​​​​​​​                        swap

                                list模拟实现整体代码​​​​​​​

---

C++：list及其模拟实现

成员函数接口总览

#include 
#include 
#include 
using namespace std;
namespace wjq
{
	//模拟实现list当中的结点类
	template 
	struct list_node
	{
		//成员函数
		list_node(const T& x = T());

		//成员变量
		list_node* _next;
		list_node* _prev;
		T _data;
	};
	//模拟实现list迭代器
	template 
	struct __list_iterator
	{
		typedef list_node node;
		typedef __list_iterator Self;
		//构造函数
		__list_iterator(node* p);
		//迭代器运算符的重载函数
		Ref operator*();
		Ptr operator->();
		Self& operator++();
		Self operator++(int);
		Self& operator--();
		Self operator--(int);
		bool operator!=(const Self& it) const;
		bool operator==(const Self& it) const;
	
		//成员变量
		node* _pnode;
	};
	//链表类
	template 
	class list
	{
	public:
		typedef list_node node;
		typedef __list_iterator iterator;
		typedef __list_iterator const_iterator;
		void empty_initialize();
		//构造函数
		list();
		//迭代器区间构造
		template 
		list(InputIterator first, InputIterator last);
		//析构函数
		~list();
		//拷贝构造
		list(const list& lt);
		//赋值运算符重载
		list& operator=(list lt);
		//插入删除函数
		void push_back(const T& x);
		void pop_back();
		void push_front(const T& x);
		void pop_front();
		iterator insert(iterator pos, const T& x);
		iterator erase(iterator pos);
		//访问容器相关函数
		T& front();
		T& back();
		const T& front() const;
		const T& back() const;
		//链表小接口
		bool empty() const;
		void clear();
		size_t size() const;
		void swap(list& lt);
		void resize(size_t n, const T& val = T());
		//普通begin(),end()迭代器
		iterator begin();
		iterator end();
		//const begin(),end()迭代器
		const_iterator begin() const;
		const_iterator end() const;
	private:
		node* _head;
		size_t _size;
	};
}

结点类的模拟实现：

构造函数

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

迭代器类的模拟实现：

构造函数

_list_iterator(node* p)
	:_pnode(p)
{}

++运算符的重载

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

--运算符的重载

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

==运算符的重载

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

!=运算符的重载

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

*运算符的重载

Ref operator*()
{
	return _pnode->_data;
}

->运算符的重载

Ptr operator->()
{
	return &_pnode->_data;
}

list的模拟实现：

默认成员函数

构造函数

void empty_initialize()
{
	_head = new node;
	_head->_next = _head;
	_head->_prev = _head;
	_size = 0;
}
//构造函数
list()
{
	empty_initialize();
}
//迭代器区间构造
template 
list(InputIterator first, InputIterator last)
{
	empty_initialize();
	while (first != last)
	{
		push_back(*first);
		++first;
	}
}

拷贝构造函数

传统写法：

void swap(list& lt)
{
	std::swap(_head, lt._head);
	std::swap(_size, lt._size);
}
list(const list& lt)
{
	empty_initialize();
	for (const auto& e : lt)//取lt的数据给e
	{
		push_back(e);
	}
}

现代写法：

void swap(list& lt)
{
	std::swap(_head, lt._head);
	std::swap(_size, lt._size);
}
list(const list& lt)
{
	list tmp(lt.begin(), lt.end());
	empty_initialize();
	swap(tmp);
}

赋值运算符重载

传统写法：

list& operator=(list lt)
{
	if (this != <)
	{
		clear();
		for (const auto& e : lt)
		{
			push_back(e);
		}
	}
	return *this;
}

现代写法：

void swap(list& lt)
{
	std::swap(_head, lt._head);
	std::swap(_size, lt._size);
}
list& operator=(list lt)
{
	swap(lt);
	return *this;
}

析构函数

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

迭代器相关函数

begin和end

//普通begin(),end()迭代器
iterator begin()
{
	return iterator(_head->_next);
}
iterator end()
{
	return iterator(_head);
}
//const begin(),end()迭代器
const_iterator begin() const
{
	return const_iterator(_head->_next);
}
const_iterator end() const
{
	return const_iterator(_head);
}

访问容器相关函数

front和back

T& front()
{
	return *begin();
}
T& back()
{
	return *(--end());
}
const T& front() const
{
	return *begin();
}
const T& back() const
{
	return *(--end());
}

插入、删除函数

insert

iterator insert(iterator pos, const T& x)
{
	node* newnode = new node(x);
	node* cur = pos._pnode;
	node* prev = cur->_prev;
	newnode->_prev = prev;
	newnode->_next = cur;
	prev->_next = newnode;
	cur->_prev = newnode;
	++_size;
	return iterator(newnode);
}

erase

iterator erase(iterator pos)
{
	assert(!empty());
	node* prev = pos._pnode->_prev;
	node* next = pos._pnode->_next;
	prev->_next = next;
	next->_prev = prev;
	delete pos._pnode;
	--_size;
	return iterator(next);
}

push_back和pop_back

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

push_front和pop_front

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

其他函数

size

size_t size() const
{
	return _size;
}

resize

resize函数的规则：

1.若当前容器的size小于所给n，则尾插结点，直到size等于n为止

2.若当前容器的size大于所给n，则只保留前n个有效数据

resize函数的实现方法：

设置一个变量n，用于记录当前所遍历的数据个数，然后开始遍历容器

void resize(size_t n, const T& val = T())
{
	iterator cur = begin();
	size_t len = 0;
	while (len < n && cur != end())
	{
		++len;
		++cur;
	}
	if (len == n)
	{
		while (cur != end())
		{
			cur = erase(cur);
		}
	}
	else
	{
		while (len < n)
		{
			push_back(val);
			++len;
		}
	}
}

clear

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

empty

bool empty() const
{
	return _head->_next == _head;
}

swap

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

list模拟实现整体代码：

#include 
#include 
#include 
using namespace std;
namespace wjq
{
	template 
	struct list_node
	{
		list_node(const T& x = T())
			:_next(nullptr)
			, _prev(nullptr)
			, _data(x)
		{}

		list_node* _next;
		list_node* _prev;
		T _data;
	};
	//用类封装普通/const迭代器
	template 
	struct __list_iterator
	{
		typedef list_node node;
		typedef __list_iterator Self;
		//构造函数
		__list_iterator(node* p)
			:_pnode(p)
		{}
		//迭代器运算符的重载
		Ref operator*()
		{
			return _pnode->_data;
		}
		Ptr operator->()
		{
			return &_pnode->_data;
		}
		Self& operator++()
		{
			_pnode = _pnode->_next;
			return *this;
		}
		Self operator++(int)//后置++
		{
			Self tmp(*this);
			_pnode = _pnode->_next;
			return tmp;
		}
		Self& operator--()
		{
			_pnode = _pnode->_prev;
			return *this;
		}
		Self operator--(int)//后置--
		{
			Self tmp(*this);
			_pnode = _pnode->_prev;
			return tmp;
		}
		bool operator!=(const Self& it)const
		{
			return _pnode != it._pnode;
		}
		bool operator==(const Self& it)const
		{
			return _pnode == it._pnode;
		}
        //成员变量
		node* _pnode;
	};
	//链表类
	template 
	class list
	{
	public:
		typedef list_node node;
		typedef __list_iterator iterator;
		typedef __list_iterator const_iterator;
		void empty_initialize()
		{
			_head = new node;
			_head->_next = _head;
			_head->_prev = _head;
			_size = 0;
		}
		//构造函数
		list()
		{
			empty_initialize();
		}
		//迭代器区间构造
		template 
		list(InputIterator first, InputIterator last)
		{
			empty_initialize();
			while (first != last)
			{
				push_back(*first);
				++first;
			}
		}
		//析构函数
		~list()
		{
			clear();
			delete _head;
			_head = nullptr;
		}
		//拷贝构造
		list(const list& lt)
		{
			list tmp(lt.begin(), lt.end());
			empty_initialize();
			swap(tmp);
		}
		void swap(list& lt)
		{
			std::swap(_head, lt._head);
			std::swap(_size, lt._size);
		}
        //赋值运算符重载
		list& operator=(list lt)
		{
			swap(lt);
			return *this;
		}
		//插入删除函数
		void push_back(const T& x)
		{
			insert(end(), x);
		}
		void pop_back()
		{
			erase(--end());
		}
		void push_front(const T& x)
		{
			insert(begin(), x);
		}
		void pop_front()
		{
			erase(begin());
		}
		iterator insert(iterator pos, const T& x)
		{
			node* newnode = new node(x);
			node* cur = pos._pnode;
			node* prev = cur->_prev;
			newnode->_prev = prev;
			newnode->_next = cur;
			prev->_next = newnode;
			cur->_prev = newnode;
			++_size;
			return iterator(newnode);
		}
		iterator erase(iterator pos)
		{
			assert(!empty());
			node* prev = pos._pnode->_prev;
			node* next = pos._pnode->_next;
			prev->_next = next;
			next->_prev = prev;
			delete pos._pnode;
			--_size;
			return iterator(next);
		}
        //访问容器相关函数
		T& front()
		{
			return *begin();
		}
		T& back()
		{
			return *(--end());
		}
		const T& front() const
		{
			return *begin();
		}
		const T& back() const
		{
			return *(--end());
		}
		//链表小接口
		bool empty()const
		{
			return _head->_next == _head;
		}
		void clear()
		{
			iterator it = begin();
			while (it != end())
			{
				it = erase(it);
			}
		}
		size_t size()const
		{
			return _size;
		}
		void resize(size_t n, const T& val = T())
		{
			iterator cur = begin();
			size_t len = 0;
			while (len < n && cur != end())
			{
				++len;
				++cur;
			}
			if (len == n)
			{
				while (cur != end())
				{
					cur = erase(cur);
				}
			}
			else
			{
				while (len < n)
				{
					push_back(val);
					++len;
				}
			}
		}
		//普通begin(),end()迭代器
		iterator begin()
		{
			return iterator(_head->_next);
		}
		iterator end()
		{
			return iterator(_head);
		}
		//const begin(),end()迭代器
		const_iterator begin()const
		{
			return const_iterator(_head->_next);
		}
		const_iterator end()const
		{
			return const_iterator(_head);
		}
    private:
		node* _head;
		size_t _size;
	};
}