根据下列 Vector 类定义，编程完成 Vector 类的具体实现：
#include "iostream.h"
class Vector
{
friend ostream &operator<<(ostream &out, const Vector &v);
private:
int *data;
int size;
public:
Vector(int v[]);
~Vector();
Vector(const Vector &v);
Vector &operator=(const Vector &v);
int &operator[](int index);
};
