#include <iostream>

using namespace std;

class B
{
public:
  B ( void );
  virtual ~B ( void );           //遵循1
  virtual void f ( int a ) = 0;
protected:
  B ( const B & );
  B &operator = ( const B & );
};
B::B ( void )
{
}
B::~B ( void )
{
}

class D : public B
{
public:
  D ( void );
  explicit D ( int a );
  virtual ~D ( void );           //遵循2
  virtual void f ( int a );
private:
  int *md;
  D ( const D & );
  D &operator = ( const D & );
};
D::D ( int a ) : B ( ), md ( new int )
{
  *md = a;
}
void D::f ( int a )
{
  *md = a;
}
D::~D ( void )
{
  delete md;
  md = NULL;
}

int main ( void )
{
  B *d = new D ( 1 );
  d->f ( 2 );
  delete d;
  d = NULL;

  return ( 0 );
}