#include <iostream>

using namespace std;

template <typename T>
class Myvector
{
    private:
        T * first;
        T * last;
        T * end;

public:
    //构造函数
    Myvector(){
        first = nullptr;
        last = nullptr;
        end = nullptr;
    }

    //析构函数
    ~Myvector(){
        delete [] first;
    }

    //拷贝构造
    Myvector(const Myvector& other){
        int size = other.size();
        first = new T[size];
        last = first + size;
        end = last;
        for(int i = 0; i < size; i++){
            first[i] = other.first[i];
        }
    }

    //拷贝赋值
    Myvector &operator=(const Myvector &other){
        if(this != &other){
            delete [] first;
            int size = other.size();
            first = new T[size];
            last = first + size;
            end = last;
            for(int i = 0; i < size; i++){
                first[i] = other.first[i];
            }
        }
    }

    //T &at(int index)
    T &at(int index){
        return first[index];
    }

    //empty()
    bool my_empty(){
        return first == last;
    }

    //full()
    bool my_full(){
        return last == end;
    }

    //front()
    T &my_front(){
        return *first;
    }

    //back()
    T &my_back(){
        return *last;
    }

    //size()
    int my_size(){
        return last - first;
    }

    //clear()
    void my_clear(){
        last = first;
    }

    //expand()二倍扩容函数
    void expand(){
        int size = this->my_size();
        T *newfirst = new T[size*2];
        memcpy(newfirst, first,sizeof(T)*(end-first));
        delete [] first;
        first = newfirst;
        newfirst = NULL;
        last = first + size;
        end = first + 2*size;
    }

    //push_back()
    void push_back(const T &data){
        *last = data;
        last++;
    }

    //pop_back()
    void pop_back(){
        if(my_empty()){
            cout << "已空，删除失败！" << endl;
            return;
        }
        last--;
    }

};


int main()
{
    //定义一个Myvector对象s
    Myvector <int> s;
    s.expand();

    //循环插入元素
    for(int i = 0; i < 20; i++){
        s.push_back(i);
    }

    //输出容器大小
    cout << "szie" << s.my_size() << endl;

    //判满
    if(s.my_full()){
        cout << "满！" << endl;
    }else{
        cout << "未满！" << endl;
    }

    //判空
    if(s.my_empty()){
        cout << "空！" << endl;
    }else{
        cout << "未空！" << endl;
    }

    //指定位置元素查询
    cout << s.at(1) << endl;
    //获取第一个和最后一个元素
    cout << "first = " << s.my_front() << "  back = " << s.my_back() << endl;
    s.my_clear();



    return 0;
}

思维导图：