#include?
#include?

using?namespace?std;
class?State;

class?Node?{
public:
????Node（State?*s）?:?state（s）?{}
????void?process（）;
????State?*state;
};

class?State?{
public:
????virtual?void?process（Node?*node）?=?0;
????virtual?~State（）?{}?//?Designed?for?inheritance
};

class?QuestionState??:?public?State?{
public:
????QuestionState（string?ques?Node?*yes?Node?*no）;
????virtual?void?process（Node?*node）;
protected:
????string?question;
????Node?*yesNode;?//?No?need?for?smart?ptrs?here
????Node?*noNode;??//?But?only?in?this?particular?case
};

class?AnswerState?:?public?State?{
public:
????AnswerState（string?a）?:?animal（a）?{}
????virtual?void?process（Node?*node）;
protected:
????string?animal;
};

void
Node::process（）
{
????state->process（this）;
}

QuestionState::QuestionState（string?q?Node?*y?Node?*n）
??:?question（q）?yesNode（y）?noNode（n）?{}

void
QuestionState::process（Node?*node）
{
????string?answer;
????cout?<????getline（cin?answer）;
????if（answer?==?“yes“）?{
????????yesNode->process（）;
????}?else?{
????????noNode->process（）