STL-模拟实现List

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在STL中的List并不单单只是一个链表，其结构设计特别精妙。

简单来说，其结构为：一个带头结点的双向循环链表。

主要代码实现：

#include <iostream>#include <assert.h>using namespace std;template<typename T>struct ListNode{ListNode* _next;ListNode* _prev;T _data;ListNode(const T& x):_data(x), _next(NULL), _prev(NULL){}};template<typename T, typename Ref, typename Ptr>  //迭代器struct ListIterator{typedef ListNode<T> Node;typedef ListIterator<T, Ref, Ptr> Self;Node* _node;ListIterator(){}ListIterator(Node* node):_node(node){}bool operator!=(const Self& s){return _node != s._node;}Ref operator*(){return _node->_data;}Ptr operator->(){return &(_node->_data);}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;}};template<typename T>class List{typedef ListNode<T> Node;public:typedef ListIterator<T, T&, T*> Iterator;typedef ListIterator<T, const T&, const T*> ConstIterator;public:List():_head(BuyNewNode(T())){_head->_next = _head;_head->_prev = _head;}~List(){Node* tmp = _head->_next;while (tmp != _head){delete tmp->_prev;tmp=tmp->_next;}_head = NULL;}void PushBack(const T& x){//Node* tmp = BuyNewNode(x);//_head->_prev->_next = tmp;//tmp->_prev = _head->_prev;//_head->_prev= tmp;//tmp->_next = _head;Insert(End(),x);}void PopBack(){Erase(--End());}void PushFront(const T& x){Insert(Begin(), x);}void PopFront(){Erase(Begin());}Iterator Insert(Iterator pos, const T& x){assert(pos._node);Node* cur = pos._node;Node* prev = cur->_prev;Node* tmp = BuyNewNode(x);prev->_next = tmp;tmp->_prev = prev;tmp->_next = cur;cur->_prev = tmp;return tmp;}Iterator Erase(Iterator pos){assert(pos._node && pos._node != _head);Node* cur = pos._node;Node* prev = cur->_prev;Node* next = cur->_next;prev->_next = next;next->_prev = prev;delete cur;cur = NULL;return next;}Iterator Begin(){//return Iterator(_head->_next);return _head->_next;}Iterator End(){return Iterator(_head);}ConstIterator Begin()const{return ConstIterator(_head->_next);}ConstIterator End()const{return ConstIterator(_head);}protected:Node* _head;private:Node* BuyNewNode(const T& x){//次处应该是空间配置器return new Node(x);}};

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