重写下面的程序，给每个类增加一个析构函数，并使类之间的关系如附件图所示，再 写出程序的输出结果。 #include <iostream> using namespace std; class base1 { public: base1() { cout << "constructing base1" << endl; } }; class base2 { public: base2() { cout << "constructing base2 " << endl; } }; class derived1 :public base2, virtual public base1 { public: derived1() { cout << "constructing derived1" << endl; } }; class derived2 :public base2, virtual public base1 { public: derived2() { cout << "constructing derived2" << endl; } }; class Derived3 :public derived1, virtual public derived2 { public: Derived3() { cout << "constructing derived3" << endl; } }; int main() { Derived3 obj; return 0; }