list 使用：
1.list 的构造：
2.list iterator的使用：
3.list capacity:
4.list element access:
5.list modifiers:
list 模拟实现：
#pragma once #include<assert.h> namespace yx { template<class T> struct list_node { list_node<T>* _next; list_node<T>* _prev; T _val; list_node(const T& val = T()) //'=T()'类似'int()'表示默认参数 :_next(nullptr) , _prev(nullptr) , _val(val) {} }; template<class T, class Ref, class Ptr> //主要用于实现普通迭代器与常量迭代器 struct __list_iterator { typedef list_node<T> Node; typedef __list_iterator<T, Ref, Ptr> self; Node* _node; __list_iterator(Node* node) :_node(node) { } Ref operator*() { return _node->_val; } Ptr operator->() { return &_node->_val; } self& operator++() { _node = _node->_next; return *this; } self operator++(int) { self tmp(*this); _node = _node->_next; return tmp; } self& operator--() { _node = _node->_prev; return *this; } self operator--(int) { self tmp(*this); _node = _node->_prev; return tmp; } bool operator==(const self& it)const { 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 iterator(_head->_next); } iterator end() { return _head; } const_iterator begin() const { return const_iterator(_head->_next); } const_iterator end() const { return const_iterator(_head); } void empty_init() { _head = new Node; _head->_prev = _head; _head->_next = _head; _size = 0; } list() { empty_init(); } 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); } list<T>& operator=(list<T> lt) { swap(lt); return *this; } ~list() { clear(); delete _head; _head = nullptr; } void clear() { iterator it = begin(); while (it != end()) { it = erase(it); } _size = 0; } void push_back(const T& x) { insert(end(), x); } void push_front(const T& x) { insert(begin(), x); } void pop_back() { erase(--end()); } void pop_front() { erase(begin()); } iterator insert(iterator pos, const T& x) { Node* cur = pos._node; Node* prev = cur->_prev; Node* newnode = new Node(x); prev->_next = newnode; newnode->_next = cur; cur->_prev = newnode; newnode->_prev = prev; ++_size; return newnode; } iterator erase(iterator pos) { assert(pos != end()); Node* cur = pos._node; Node* prev = cur->_prev; Node* next = cur->_next; prev->_next = next; next->_prev = prev; delete cur; --_size; return next; } size_t size() { return _size; } private: Node* _head; size_t _size; }; }
