STL，迭代器的C++简单实现

// Iterator.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include <Windows.h>#include <iostream>#include <string>#include <memory>using namespace std;// 对于C++，STL中已经包含迭代器的实现了// 就不再单独造车轮了// 部分代码见【STL源码剖析】// 来一个智能指针的示意namespace TEST{template<class T>class auto_ptr{public:// 显示构造函数explicit auto_ptr(T *p = NULL) : pointee(p){}template<class U>auto_ptr(auto_ptr<U>& rhs) : pointee(rhs.release()){}~auto_ptr() {delete pointee;}template<class U>auto_ptr<T>& operator=(auto_ptr<U>& rhs){if (this != &rhs){reset(rhs.release());return *this;}}T& operator*() const{return *pointee;}T* operator->() const{return pointee;}T* get() const{return pointee;}protected:T* release(){T *p = new T;memcpy(p, pointee, sizeof(T));delete this;return p;}void reset(T *p){if (pointee){delete pointee;pointee = NULL;}pointee = p;}private:T *pointee;};}// 智能指针的示例// 申请的内存不需要释放，没有内存泄露void func(){TEST::auto_ptr<string> ps(new string("Hello"));cout<< *ps <<endl;cout<< ps->size() <<endl;}namespace TEST{template<typename T>class ListItem{public:ListItem(T vl): _value(vl), _next(NULL){}T value() const {return _value;}ListItem *next() const {return _next;}void SetNext(ListItem<T> *p){_next = p;}private:T_value;ListItem*_next;};// 迭代器是一种智能指针template<typename T>class List{public:List(){ListItem<T> *a = new ListItem<T>(0);// 没有析构哦_front = a;_front->SetNext(NULL);_size = 0;}voidinsert_end(T value);voiddisplay(std::ostream &os = std::cout) const;ListItem<T> *front(){return _front;}ListItem<T> *end(){ListItem<T> *end = _front;while(1){if (end->next()){end = end->next();}else{break;}} return end;}private:ListItem<T> *_front;long _size;};template<typename T>void TEST::List<T>::display( std::ostream &os /*= std::cout*/ ) const{ListItem<T> *end = NULL;end =  _front->next();ListItem<T> *before = _front;do {os<<end->value()<<endl;end = end->next();} while (end);}// 因为只保留了链表头，所以插入操作很纠结，比较失败template<typename T>void TEST::List<T>::insert_end( T value ){ListItem<T> *node = new ListItem<T>(value);ListItem<T> *end = this->end();//end = _front;//while(1)//{//if (end->next())//{//end = end->next();//}//else//{//break;//}//} end->SetNext(node);_size ++;}template<typename Item>struct ListIter{Item *ptr;ListIter(Item *p = NULL): ptr(p){}Item& operator*() const {return *ptr;}Item* operator->() const {return ptr;}ListIter& operator++(){ptr = ptr->next();return *this;}bool operator== (const ListIter &i){return ptr == i.ptr;}bool operator!= (const ListIter &i){return ptr != i.ptr;}};}int _tmain(int argc, _TCHAR* argv[]){func();TEST::List<int>  testList;testList.insert_end(10);testList.insert_end(20);testList.insert_end(11);TEST::ListIter<TEST::ListItem<int>> iter(testList.front());// 由于链表头为空，所以最好由后往前迭代，第一个节点不能用for (; iter != testList.end(); ){++iter;std::cout<<iter->value()<<endl;}testList.display();return 0;}//输出结果：//Hello//5//10//20//11//10//20//11//请按任意键继续. . .