C++继承和派生

#include <iostream>
 using namespace std;
 class Base 
 {
   public:
   Base(int i) { 
   cout << i; 
   }
   ~Base () { }
 };
 
class Base1: virtual public Base 
 {
   public:
   Base1(int i, int j=0) : Base(j) 
   { 
   cout << i; 
   }
   ~Base1() {}
 };
 
class Base2: virtual public Base 
 {
   public:
   Base2(int i, int j=0) : Base(j) 
   { 
   cout << i; 
   }
   ~Base2() {}
 };
 
class Derived : public Base2, public Base1 
 {
   public:
   Derived(int a, int b, int c, int d) : mem1(a), mem2(b), Base1(c), 
                                          Base2(d), Base(a) 
   { 
   cout << b; 
   }
   private:
   Base2 mem2;
   Base1 mem1;
 };
 void main() 
 { 
   Derived objD (1, 2, 3, 4); 
 }