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Upload note code of chapter 3 iterator
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‎3_STL_iterator/3_1_find.cpp‎

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#include <vector>
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#include <list>
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#include <deque>
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#include <algorithm>
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#include <iostream>
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using namespace std;
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// 迭代器是㆒种行为类似指针的对象，对operator*和operator->进行重载
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int main() {
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const int arraySize = 7;
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int ia[arraySize] = {0, 1, 2, 3, 4, 5, 6};
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vector<int> ivect(ia, ia + arraySize);
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list<int> ilist(ia, ia + arraySize);
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deque<int> ideque(ia, ia + arraySize);
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vector<int>::iterator it1 = find(ivect.begin(), ivect.end(), 4);
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if (it1!=ivect.end())
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cout << "4 not found." << endl;
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else
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cout << "4 found. " << *it1 << endl;
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list<int>::iterator it2 = find(ilist.begin(), ilist.end(), 6);
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if (it2!=ilist.end())
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cout << "6 not found." << endl;
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else
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cout << "6 found. " << *it2 << endl;
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deque<int>::iterator it3 = find(ideque.begin(), ideque.end(), 8);
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if (it3!=ideque.end())
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cout << "8 not found." << endl;
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else
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cout << "8 found. " << *it3 << endl;
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}

‎3_STL_iterator/3_2_algorithm.h‎

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template <class InputIterator, class T>
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InputIterator find(InputIterator first, InputIterator last, const T& value) {
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// 修改*first!=value
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while (first!=last && *first!=value)
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// while (first!=last && (*first).value()!=value)
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++first;
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return first;
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}
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template <class InputIterator, class Function>
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InputIterator for_each(InputIterator first, InputIterator last, Function f) {
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for (; first != last; ++first)
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f(*first);
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return first;
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}

‎3_STL_iterator/3_2_autoptr.cpp‎

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// file: 3autoptr.cpp
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template <class T>
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class auto_ptr {
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public:
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explicit auto_ptr(T *p = 0) : pointee(p) {}
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template <class U>
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auto_ptr(auto_ptr<U>& rhs): pointee(rhs.release()) {}
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~auto_ptr() {
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delete pointee;
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}
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template <class U>
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auto_ptr<T>& operator=(auto_ptr<U>& rhs) {
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if (this != &rhs)
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reset(rhs.release());
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return *this;
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}
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T& operator*() const {
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return *pointee;
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}
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T* operator->() const {
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return pointee;
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}
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T* get() const {
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return pointee;
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}
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private:
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T *pointee;
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};

‎3_STL_iterator/3_2_mylist-iter-test.cpp‎

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// file: 3mylist-iter-test.cpp
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#include "3_2_algorithm.h"
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#include "3_2_mylist-iter.h"
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#include "3_2_mylist.h"
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using namespace std;
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//为了完成一个针对 List而设计的迭代器，我们无可避免曝露了太多 List细节：
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// 在 main()为了制作 begin和 end两个迭代器，我们曝露了 ListItem；
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// 在 ListIter class 为了达成 operator++的目的，我们曝露了 ListItem的操作函式 next()。
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// 如果不是为了迭代器，ListItem 原本应该完全隐藏起来不曝光的。
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// 换句话说，要设计出 ListIter，首先必须对 List 的细节有非常丰富的了解。
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// 既然这无可避免，干脆就把迭代器的开发工作交给 List的设计者好了，
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// 如此一来所有细节反而得以封装起来不被使用者看到。
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// 这正是为什么每一种 STL 容器都提供有专属迭代器的缘故。
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// 如果不写全局比较函数，则需要更改find函数判定
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template <typename T> bool operator!=(const ListItem<T>& item, T n) {
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return item.value() != n;
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}
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int main() {
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List<int> mylist;
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for (int i = 0; i < 5; ++i) {
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mylist.insert_front(i);
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mylist.insert_end(i + 2);
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}
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mylist.display();
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ListIter<ListItem<int>> begin(mylist.front());
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ListIter<ListItem<int>> end;
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ListIter<ListItem<int>> iter;
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iter = find(begin, end, 3);
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if (iter == end)
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cout << "not found" << endl;
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else
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cout << "found. " << iter->value() << endl;
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iter = find(begin, end, 7);
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if (iter == end)
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cout << "not found" << endl;
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else
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cout << "found. " << iter->value() << endl;
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}

‎3_STL_iterator/3_2_mylist-iter.h‎

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// file: 3mylist-iter.h
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// #include "3_2_mylist.h"
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template <class Item>
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struct ListIter {
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Item *ptr; // 保持与容器的联系
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// default ctor
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ListIter(Item* p =0) : ptr(p) {}
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// 解引用 dereference
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Item& operator*() const {
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return *ptr;
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}
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// member access
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Item* operator->() const {
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return ptr;
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}
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// prefix increment, 返回对象
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ListIter& operator++() {
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ptr = ptr->next();
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return *this;
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}
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// postfix increment, 返回值（新对象）
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// int为占位符，提示编译器这是后自增
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ListIter operator++(int) {
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ListIter temp = *this;
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++*this; // 调用前面的前自增
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return temp;
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}
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bool operator==(const ListIter& i) const {
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return ptr == i.ptr;
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}
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bool operator!=(const ListIter& i) const {
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return ptr != i.ptr;
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}
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};

‎3_STL_iterator/3_2_mylist.h‎

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// file: 3mylist.h
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#include <iostream>
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// 先声明
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template <typename T>
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class ListItem;
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template <typename T>
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class List {
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// 定义public以供访问
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public:
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void insert_front(T value);
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void insert_end(T value);
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void display(std::ostream &os = std::cout) const;
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ListItem<T> * front() {
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return _front;
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}
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List();
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private:
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ListItem<T> *_end;
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ListItem<T> *_front;
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long _size;
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};
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// 自己实现
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template <typename T>
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List<T>::List() {
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_size = 0;
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_front = NULL;
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_end = NULL;
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}
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template <typename T>
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void List<T>::insert_front(T value) {
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ListItem<T>* temp = new ListItem<T>(value);
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temp->set_next(_front);
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_front = temp;
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_size++;
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}
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template <typename T>
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void List<T>::insert_end(T value) {
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ListItem<T>* temp = new ListItem<T>(value);
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ListItem<T> *last = _front;
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while (last->next() != _end)
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last = last->next();
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last->set_next(temp);
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_end = temp->next();
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_size++;
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}
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// 声明写了默认参数后定义不能重写
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template <typename T>
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void List<T>::display(std::ostream &os) const {
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ListItem<T> *temp = _front;
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while (temp!= _end) {
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std::cout << temp->value() << " ";
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temp = temp->next();
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}
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std::cout << std::endl;
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}
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template <typename T>
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class ListItem {
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public:
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T value() const {
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return _value;
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}
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ListItem* next() const {
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return _next;
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}
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void set_next(ListItem* i) {
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_next = i;
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}
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ListItem(T value) : _value(value) {
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_next = NULL;
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}
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private:
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T _value;
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ListItem *_next;
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};

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