动态继承

# include <iostream>using namespace std;struct A{int a;A(){cout<<"I am A"<<endl;a=1;}~A(){cout<<"I am A destruct"<<endl;}};struct B:public A{B(){cout<<"I am B"<<endl;a=0;}~B(){cout<<"I am B destruct"<<endl;}};int main(){    B *b=new B;A *q=b;cout<<q->a<<endl;}