【C++模拟实现】list的模拟实现

list模拟实现的部分代码

namespace test
{template<class T>struct list_node//默认公有{list_node<T>* _next;list_node<T>* _prev;T _val;list_node(const T& val = T()):_next(nullptr),_prev(nullptr),_val(val){}};template<class T,class Ref,class Ptr>struct __list_iterator{typedef list_node<T> Node;typedef __list_iterator<T, Ref, Ptr> Self;Node* _node;__list_iterator(Node* node=nullptr):_node(node){}__list_iterator(const Self&l):_node(l._node){}Ref operator*(){return _node->_val;}Ptr operator->(){return &_node->_val;}Self& operator++(){_node=_node->_next;return *this;}Self& operator++(int){Self tmp(_node);return tmp;}Self& operator--() {_node=_node->_prev;return *this;}Self& operator--(int) {Self tmp(*this);_node=_node->_prev;return *this;}bool operator!=(const Self& it) const//引用时一定要注意是否要加上const，防止权限放大，这里需要加上！！！{return _node!=it._node;}bool operator==(const Self& it) const{return _node==it._node;}};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;iterator begin(){//return _head->_next;return iterator(_head->_next);}iterator end(){//return _head;return iterator(_head);}list(){_head=new Node;_head->_prev=_head;_head->_next=_head;}~list(){clear();delete _head;_head=nullptr;}void clear(){iterator it = begin();while(it!=end()){it=erase(it);}}void push_back(const T& x){insert(end(),x);//注意这里是end(),不是end()-1;}void pop_back(){erase(--end());}iterator insert(iterator pos, const T& x){Node*newnode = new Node(x);pos._node->_prev->_next=newnode;newnode->_prev=pos._node->_prev;newnode->_next=pos._node;pos._node->_prev=newnode;return newnode;}iterator erase(iterator pos){Node*tmp=pos._node;Node*next=tmp->_next;tmp->_prev->_next=tmp->_next;tmp->_next->_prev=tmp->_prev;delete tmp;tmp = nullptr;return next;}private:Node* _head;};
}