1.什么是迭代器？
用来遍历容器，访问容器数据。
2.迭代器使用
1.初始化
//初始化 list<int> mylist;//list的整数对象 list<int>::iterator iter;//list内部类，迭代器对象(正向输出) list<int>::reverse_iterator riter;//list内部类，迭代器对象(反向输出) int array[5] = { 1,2,3,4,5 };2.添加数据
//添加数据到list中 mylist.assign(array, array + 5);3.正向输出
//正向输出 for (iter = mylist.begin();iter != mylist.end();iter++) { cout << *iter << "\t" ; }4.反向输出
for (riter = mylist.rbegin();riter != mylist.rend();riter++) { cout << *riter << "\t"; }结果：
3.实现一个反向迭代器
1.建立一个节点（用来存储数据）
template<class type> struct Node { type data; Node<type>* left; Node<type>* right; Node(type data):data(data),left(nullptr),right(nullptr){} Node(type data, Node<type>*left, Node<type>*right) :data(data) ,left(left),right(right){} };2.事项简单的list类（类中包括一个反方向的迭代器）
template<class type> class list { public: list() {} //因为需要反向迭代，所以需要建立双链表 void assign(type* begin,type* end) { while (begin != end) { Node<type>* node = new Node<type>(*begin); if (size == 0) { listhead = node; listend = node; node->left = node; node->right = node; } else { listend->right = node; node->right = listhead; node->left = listend; listend = node; listhead->left = node; } size++; begin++; } } //rbegin,rend Node<type>* rbegin() { return listend; } Node<type>* rend() { return listhead; } //反方向的迭代器----------------------------------------- class reverse_iterator { public: void operator=(Node<type>* node) { this->pmove = node; } bool operator!=(Node<type>* node) { return this->pmove != node; } reverse_iterator& operator++(int) { this->pmove = this->pmove->left; return (*this); } type operator*() { return this->pmove->data; } protected: Node<type>* pmove; }; protected: Node<type>* listhead; Node<type>* listend; int size=0; };3.对上述代码的解释
（1）插入代码，普通指针指向修改
//因为需要反向迭代，所以需要建立双链表 void assign(type* begin,type* end) { while (begin != end) { Node<type>* node = new Node<type>(*begin); if (size == 0) { listhead = node; listend = node; node->left = node; node->right = node; } else { listend->right = node; node->right = listhead; node->left = listend; listend = node; listhead->left = node; } size++; begin++; } }（2）单目运算符的重载一般在类中直接实现，使用友元函数会增加传参
class reverse_iterator { public: void operator=(Node<type>* node) { this->pmove = node; } bool operator!=(Node<type>* node) { return this->pmove != node; } reverse_iterator& operator++(int) { this->pmove = this->pmove->left; return (*this); } type operator*() { return this->pmove->data; } protected: Node<type>* pmove; };结果：
整个代码： 瑕疵之处
1.析构函数没有使用，目前不太清楚应该在哪里开始析构。
2.数据1输出不出来，因为下面代码在头节点会报0。
解决方法：使用一个头节点（不存放数据）
bool operator!=(Node<type>* node) {
return this->pmove != node;
}附上总体代码
1.main
#include"标头.h" #include<iostream> #include<stdlib.h> using namespace std; int main() { //list链表 反向输出 迭代器 list<int>::reverse_iterator riter; //list<int> mylist = { 1,2,3,4,5,6 }; int arr[6] = { 1,2,3,4,5,6 }; list<int> mylist; mylist.assign(arr, arr + 6); for (riter = mylist.rbegin();riter != mylist.rend();riter++) { cout << *riter << "\t"; } cout << endl; return 0; }2.实现
#define _CRT_SECURE_NO_WARNINGS #include<iostream> #include<stdlib.h> using namespace std; template<class type> struct Node { type data; Node<type>* left; Node<type>* right; Node(type data):data(data),left(nullptr),right(nullptr){} Node(type data, Node<type>*left, Node<type>*right) :data(data) ,left(left),right(right){} }; template<class type> class list { public: list() {} //因为需要反向迭代，所以需要建立双链表 void assign(type* begin,type* end) { while (begin != end) { Node<type>* node = new Node<type>(*begin); if (size == 0) { listhead = node; listend = node; node->left = node; node->right = node; } else { listend->right = node; node->right = listhead; node->left = listend; listend = node; listhead->left = node; } size++; begin++; } } //rbegin,rend Node<type>* rbegin() { return listend; } Node<type>* rend() { return listhead; } class reverse_iterator { public: void operator=(Node<type>* node) { this->pmove = node; } bool operator!=(Node<type>* node) { return this->pmove != node; } reverse_iterator& operator++(int) { this->pmove = this->pmove->left; return (*this); } type operator*() { return this->pmove->data; } protected: Node<type>* pmove; }; protected: Node<type>* listhead; Node<type>* listend; int size=0; };
