Как поместить в STL-контейнер экземпляры разных классов?

///////////////////////////////////////////////////////////
#include <vector>
///////////////////////////////////////////////////////////
struct A
{
    virtual ~A() {};
};
 
struct B : A
{
    //some code
};
 
int main()
{
    std::vector< A* > vec;
    vec.push_back( new B() );
}

std::vector<void*> ve;
        ve.push_back((void*)new int(3));
        ve.push_back((void*)new std::string("hello"));
        std::cout<<*(int*)ve.at(0)<<" "<<*(std::string*)ve.at(1)<<std::endl;

#include<boost/variant.hpp>
 
struct my_struct {
    friend std::ostream& operator<<(std::ostream& os, my_struct& t) {
        os<<"my_struct";
        return os;
    }
};
 
struct visit : public boost::static_visitor<>
{
    template<typename T>
    void operator()(T& t) const {
        std::cout<<t<<std::endl;
    }
};
 
int main() {
using variant = boost::variant<std::string, my_struct, int, float>;
        std::vector<variant> ve;
        ve.push_back(2.f);
        ve.push_back(1);
        ve.push_back(std::string("hello"));
        ve.push_back(my_struct{});
        std::for_each(std::begin(ve), std::end(ve), [=](auto el) {boost::apply_visitor(visit(), el);});
}