Multiple inheritance

使用类似Java的接口类可以避免虚继承带来的开销

#include <iostream>

using namespace std;

class A {
    virtual void a() = 0;
};

class B : public A {
    virtual void b() = 0;
};

class C : public A {
    virtual void c() = 0;
};

class D : public B, public C {
public:
    void a() { cout << "a\n"; }
    void b() {}
    void c() {}
};

int main() {
    D d;
    d.a();
    return 0;
}