C++继承应用例程

#include <iostream>
#include <cstring>
using namespace std;

class NameString{//声明类namestring
private:
    char *str;
public:
    //声明构造函数,不能有返回类型
    NameString(char *s="...")
    {
        str = new char[strlen(s)+1]; 
        strcpy(str,s);
//        cout<<"构造 NameString OK!"<<endl;
    }
    //声明成员函数
    void print()
    {
        cout<<str;//打印私有成员
    }
    //析构函数,不能有返回类型和形参
    ~NameString()
    {
//        cout<<"析构 NameString OK!"<<endl;
        delete str;
    }
};

class Student{ //声明类
protected:
    int StudentNO;
    NameString Name;//类类型的成员变量
    int Scores;
    static int total_Scores;//静态成员变量
    static int total_Num;
public:
    //以列表形式初始化
    Student(int a,char *b,int c):StudentNO(a),Name(b),Scores(c)
    {
        total_Scores += c;
        total_Num++;
//        cout<<"构造 Student OK!"<<endl;
    }

    void print()
    {
        cout<<StudentNO<<'\t';
        Name.print();//这是一个类类型的成员变量,本类不能直接访问string类的成员
        cout<<'\t'<<Scores<<endl;
    }

    void average()
    {
        cout<<"Average:"<<total_Scores/total_Num<<endl;
    }

    static void total_disp()//静态成员函数
    {
        cout<<"Total_Scores:"<<total_Scores<<endl;
        cout<<"Total_Num:"<<total_Num<<endl;
    }

};

class Graduate:public Student{
private:
    char *teacher;
public:
    Graduate(int a,char *b,int c,char *s):Student(a,b,c)
    {
        teacher = new char[strlen(s)+1];
        strcpy(teacher,s);
    }
    ~Graduate()
    {
        delete teacher;
    }

    void print()
    {
        cout<<StudentNO<<'\t';
        Name.print();//这是一个类类型的成员变量,本类不能直接访问string类的成员
        cout<<'\t'<<Scores;
        cout<<'\t'<<teacher<<endl;
    }
};
//定义静态成员变量,并进行初始化
int Student::total_Scores = 0;
int Student::total_Num = 0;

int main()
{
    Graduate st1(1,"wen",94,"chin");
    Graduate st2(2,"hao",100,"chin");
    Graduate st3(3,"lin",100,"chin");
#if 0
    Student st1(1,"wen",94,"chin");
    Student st2(2,"hao",100,"chin");
    Student st3(3,"lin",100,"chin");
#endif
    cout<<"学号"<<'\t'<<"姓名"<<'\t'<<"成绩"<<'\t'<<"导师"<<endl;
    st1.print();
    st2.print();
    st3.print();

    Student::total_disp();

    st1.average();

    return 0;

}