list库实现

list库实现的要点：

构建list类时，需要同时构建struct Node来存储节点信息，list类中只存储哨兵位节点信息，迭代器类需要template<T,Ptr,Ref>来构建const和非const迭代器，迭代器中也是存储节点信息。反向迭代器也是同样道理，但是可以用迭代器来构建反向迭代器。具体代码如下 

#include<iostream>
#include<assert.h>
#include<algorithm>
using namespace std;

template<class T>
struct __list_node
{
__list_node(const T& val = T())
:_data(val)
,_prev(nullptr)
,_next(nullptr)
{}

__list_node* _prev;
__list_node* _next;
T _data;
};//构建每个节点

//构建迭代器struct
template<class T, class Ptr, class Ref>
struct __list_iterator
{
typedef __list_node<T> Node;
typedef __list_iterator<T, Ptr, Ref> Self;
Node* _node;//成员变量还是节点，只是在成员函数做手脚
__list_iterator(Node* val )
:_node(val)
{}

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

Ptr operator->()
{
return &(_node->_data);
}
Ref operator*()
{
return _node->_data;
}
bool operator!= ( const Self& val )
{
return !(_node == val._node);
}


};
template<class T,class Ptr,class Ref>
struct __list_reverse_iterator
{
typedef __list_iterator<T, T*, T&> iterator;
typedef __list_reverse_iterator<T, T*, T&> Self;
iterator _it;
__list_reverse_iterator(iterator it)
:_it(it)
{}
Self operator++()
{
_it = _it._node->_prev;
return *this;
}
T& operator*()
{
return _it._node->_data;
}
bool operator!=(const Self& rit)
{
return !(_it._node == rit._it._node);
}

};

//构建双向带头循环链表
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;
typedef __list_reverse_iterator<T, T*, T&> reverse_iterator;
reverse_iterator rbegin()
{
return reverse_iterator(--end());
}
reverse_iterator rend()
{
return reverse_iterator(end());
}
iterator begin()
{
return iterator(_phead->_next);
}
const_iterator begin()const
{
return const_iterator(_phead->_next);
}
iterator end()
{
return iterator(_phead);
}
const_iterator end()const
{
return const_iterator(_phead);
}

list()//开头空间，初始化
{
_phead = new Node;
_phead->_next = _phead;
_phead->_prev = _phead;
}
~list()
{
clear();
delete _phead;
_phead = nullptr;
}
//拷贝构造(先创建一个哨兵位，然后再pushback)
list(const list<T>& l)
{
_phead = new Node;
_phead->_next = _phead;
_phead->_prev = _phead;
for (auto& x : l)
{
push_back(x);
}
}
list<T>& operator=(const list<T>& l)
{
list<T> tmp(l);
swap(_phead, tmp._phead);
return *this;
}

//尾插入
void push_back(const T& val)
{
//Node* tail = _phead->_prev;
//Node* newnode = new Node(val);
更变链接
//tail->_next = newnode;
//newnode->_prev = tail;
//newnode->_next = _phead;
//_phead->_prev = newnode;
insert(end(), val);
}
//头插
void push_front(const T& val)
{
insert(begin(), val);
}
//头删除
void pop_front()
{
erase(begin());
}
//尾删除
void pop_back()
{
erase(--end());
}
//清空节点(除了哨兵位，都清除)
void clear()
{
iterator it = begin();
while (it != end())
{
it = erase(it);
}
}
//随机插入
void insert(iterator pos, const T& val)
{
Node* pcur = pos._node;
Node* prev = pcur->_prev;
Node* newnode = new Node(val);
//构建联系
newnode->_prev = prev;
newnode->_next = pcur;
prev->_next = newnode;
pcur->_prev = newnode;

}
//删除指定位置(不能将哨兵位删掉！！
iterator erase(iterator pos)
{
assert(pos != end());
Node* pcur = pos._node;
Node* prev = pcur->_prev;
Node* next = pcur->_next;
delete pcur;
pcur = nullptr;
prev->_next = next;
next->_prev = prev;
return iterator(next);
}

private:
Node* _phead;
};

原文地址：https://blog.csdn.net/klausur31/article/details/142798403

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