qingwenclass Component{public:    virtual void foo() = 0;};class LeafA : public Component{public:    // Interface.    virtual void foo() override { cout <<"LeafA::foo()." <
     
       m_components;public:    // Interface.    virtual void foo() override { for (auto i : m_components) { i->foo(); } }    void add(Component *component) { m_components.push_back(component); }};int main(int argc, char *argv[]){    Composite *c1 = new Composite, *c2 = new Composite, *c = new Composite;    c1->add(new LeafA);    c2->add(new LeafA), c2->add(new LeafB);    c->add(c1), c->add(c2);     // 这里体现了 Composite 模式的优势。                                 // 不区别对待单个 Leaf 和 Composite。                                // 使得递归每一个 Component 变得容易。    c->foo();        return 0;}