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#include <iostream>

using namespace std;

template <typename T>

class myvector

{

private:

    T* begin; //指向头的指针

    T* end;   //指向数据的尾部的指针

    T* last;   //指向数据最大容量下标的指针

public:

    myvector(){}  //无参构造

    myvector(int a,const T &b)

    {

        begin=new T[a];

        for(int i=0;i<a;i++)

        {

            begin[i]=b;

        }

        last=begin+a;

        end=begin+a;

    } //有参构造

    ~myvector()   //析构函数

    {

        delete []begin;

        begin=end=last=nullptr;

    }

    myvector(const myvector &other)

    {

        T* temp=new T[other.last-other.begin];

        int a=other.last-other.begin;

        memcpy(temp,other.begin,sizeof(T)*a);

        delete []begin;

        begin=temp;

        end=begin+a;

        last=begin+a;

    }            //拷贝构造

    myvector &operator=(myvector &other)  //拷贝赋值

    {

        T* temp=new T[other.last-other.begin];

        int a=other.last-other.begin;

        memcpy(temp,other.begin,sizeof(T)*a);

        delete []begin;

        begin=temp;

        end=begin+a;

        last=begin+a;

        return *this;

    }

    T at(int a)    //at函数

    {

        if(a<0&&a>last-begin)

        {

            cout<<"下标超长"<<endl;

            throw(-1);

        }

        else

            return *(begin+a) ;

    }

    bool empty()   //判空

    {

        return begin==end;

    }

    bool full()     //判满

    {

        return end==last;

    }

    T front()       //访问第一个元素

    {

        return *begin;

    }

    T back()       //访问最后一个元素

    {

        return *end;

    }

     int size()     //容纳的元素个数

     {

        return last-begin+1;

     }

     void clear()     //清空

     {

        while(last!=begin)

        {

            pop_back();

        }

     }

     void expand()   //二倍扩容

     {

        T* temp=new T[2*(last-begin)];

        int s1=last-begin+1;

        int a=last-begin;

        memcpy(temp,begin,sizeof(T)*a);

        memcpy(temp,begin,sizeof (T)*s1);

        delete []begin;

        begin=temp;

        end=begin+a;

        last=begin+2*a;

     }

     void push_back(T other)  //将元素添加到尾部

     {

         if(end==last)

             {

                expand();

             }        //二倍扩容

         *(end++)=other;

     }

    void pop_back()

    {

        if(end==begin)

            cout<<"删除失败，容器为空";

        else

            end--;

    } //将尾部元素删除

    void show()

    {

        for(T*i=begin;i<=end;i++)

        {

            cout<<*i<<endl;

        }

    }

};

int main()

{

    myvector<int>s1(6,5);

    s1.push_back(3);

    s1.push_back(4);

    myvector<int>s2(s1);

    myvector<int>s3=s1;

    s1.show();

}