写一个baseclass 和它派生出的drivedclass ，通过指针调用二者相同的函数

#include<bits/stdc++.h>
using namespace std;
class BaseClass
{
public:
    void fn1()
    {
        printf("fn1 in BaseClass\n");
    }
    void fn2()
    {
        printf("fn2 in BaseClass\n");
    }
};
class DerivedClass :public BaseClass
{
public:
     void fn1()
    {
        printf("fn1 in DerivedClass\n");
    }
    void fn2()
    {
        printf("fn2 in DerivedClass\n");
    }
} ;
int main()
{
    DerivedClass a;
    DerivedClass *p1=&a;
    BaseClass b;
    BaseClass *p2=&b;
    a.fn1();
    a.fn2();
    p1->DerivedClass::fn1();
    p1->BaseClass::fn1();
    p2->fn1();
    p2->fn2();
    return 0;
}