c++ class 题目求教 急!!!

c++ class 题目求教 急!!!

// problem 1
#include
using std::cout;
using std::endl;

class first_class;

class third_class {
public:
third_class() {}
void print(const first_class &fc);
};

class first_class {
friend class second_class;
friend void third_class::print(const first_class &);
public:
first_class(int d) : data(d) {}
void print() const { cout << data << endl; }
private:
int data;
};

class second_class {
public:
second_class(int d) : fc(d) {}
void print() { cout << fc.data << endl; }
first_class get() { return fc; }
private:
first_class fc;
};

void third_class::print(const first_class &fc) {
fc.print();
}

int main() {
second_class sc(1);
sc.print();

third_class tc;
tc.print(sc.get());
return 0;
}

// problem 2
#include
using std::cout;
using std::endl;

class Hen {
public:
Hen() {}
void display() {
Nest nest(1);
cout << "I am a hen" << endl;
cout << nest.egg.egg_data << endl;
nest.display();
}

private:
class Nest {
friend class Hen;
public:
Nest(int i) : egg(i) {}
void display() {
cout << "I am a nest" << endl;
cout << egg.egg_data << endl;
egg.display();
}
private:
class Egg {
friend class Hen;
friend class Nest;
public:
Egg(int n) : egg_data(n) {}
void display() {
cout << "I am an egg" << endl;
}
private:
int egg_data;
};

Egg egg;
};
};

int main() {
Hen hen;
hen.display();

return 0;
}

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