使用c++分别定义Person类、Employee类、Student类以及在职研究生类PartTime Graduate Student，并且画出相应的继承层次图。 ..

以下是C++代码实现：

class Person {
protected:
    string name;
    int age;
public:
    Person(string n, int a) : name(n), age(a) {}
    virtual void display() {
        cout << "Name: " << name << ", Age: " << age << endl;
    }
};

class Employee : public Person {
protected:
    int salary;
public:
    Employee(string n, int a, int s) : Person(n, a), salary(s) {}
    void display() {
        Person::display();
        cout << "Salary: " << salary << endl;
    }
};

class Student : public Person {
protected:
    string major;
public:
    Student(string n, int a, string m) : Person(n, a), major(m) {}
    void display() {
        Person::display();
        cout << "Major: " << major << endl;
    }
};

class PartTimeGraduateStudent : public Employee, public Student {
protected:
    string researchTopic;
public:
    PartTimeGraduateStudent(string n, int a, int s, string m, string r) : Employee(n, a, s), Student(n, a, m), researchTopic(r) {}
    void display() {
        Employee::display();
        Student::display();
        cout << "Research Topic: " << researchTopic << endl;
    }
};

以下是继承层次图：

           +-------+
           | Person|
           +-------+
            /     \
           /       \
          /         \
+---------+      +--------+
|Student  |      |Employee|
+---------+      +--------+
      |               |
      |               |
      |               |
+---------------------------+
|PartTimeGraduateStudent     |
+---------------------------+