仿照vector手动实现自己的myVector部分功能，最主要实现二倍扩容功能

#include <iostream>

using namespace std;
template <typename V>
class myVector
{
private:
   V *data;      //存放数据
   int size;     //数组长度
   int capacity; //容量大小
public:
   myVector():size(0),capacity(1)
   {
      data = new V[capacity];
      cout<<"无惨构造"<<endl;
   }
   ~myVector()
   {
      delete []data;
      cout<<"析构函数"<<endl;
   }
    //判空
    bool empty();
    //返回指定的位置
    V& at(int index);
    //尾插
    void push_back(int value);
    //尾删
    void pop_back();
    //任意位置插入
    void insert(int pos,const V &value);
    //当前元素个数
    int get_size();
    //二倍扩容
    int expandCapacity();




};
//判空
template <typename V>
bool myVector<V>::empty()
{
    return size==0;
}
//当前元素的个数
template <typename V>
int myVector<V>::get_size()
{
    return size;
}
//二倍扩容
template <typename V>
int myVector<V>::expandCapacity()
{
    capacity *= 2;
    V *newdata = new V[capacity]; //定义一个新的指针指向原来的空间
    for(int i=0;i<size;i++)
    {
        newdata[i] = data[i];
    }
    delete []data; //将原来的空间释放掉
    data = newdata; //再把原来的指针更新为newdata，并且data指向了新的空间
    return capacity;
}

//尾插
template <typename V>
void myVector<V>::push_back(int value)
{
    if(size>=capacity)
    {
        expandCapacity();   //调用一次二倍扩容
    }
    data[size] = value;
    size++;
}
//尾删
template <typename V>
void  myVector<V>::pop_back()
{
    if(size>0)
    {
        size--;
    }
}
//返回指定的位置
template <typename V>
V& myVector<V>::at(int index)
{
    if(index<0||index>=size)
    {
        throw V(1);
    }
    return data[index];
}
//任意位置插入
template <typename V>
void myVector<V>::insert(int pos,const V &value)
{
    if(pos<0||pos>size)
    {
        throw V("pos");
    }
    if(size>=capacity)
    {
        expandCapacity();   //调用一次二倍扩容
    }
    for(int i=size;i>pos;i--)
    {
        data[i+1] = data[i];   //整体后移
    }
    data[pos] = value;
    size++;
}
int main()
{
   int i;
   myVector<int> v1;
   cout<<v1.empty()<<endl;    //1
   v1.push_back(80);
   v1.push_back(90);
   v1.push_back(5);
   for(i=0;i<static_cast<int>(v1.get_size());i++)
   {
       cout<<v1.at(i)<<" ";
   }
   cout<<endl;
   cout<<v1.empty()<<endl;
   cout<<"v1.cap = "<<v1.expandCapacity()<<endl;
   v1.push_back(80);
   v1.push_back(90);
   v1.push_back(5);
    cout<<"v1.cap = "<<v1.expandCapacity()<<endl;
    return 0;
}