6、小作业：
用一个函数来实现一个功能，分别统计全市在校学生的平均年龄。学生包括小学生、中学生、高中生、大学生 等。用一个函数来实现！
下节课会给大家解答这个小作业，用的方法也是下节课即将要讲解的，大家先事先自己试试吧！

#include <iostream>
using namespace std;
enum Estudent
{
    Student = 0,
    Pupil,
    Middle,
    High
};
class C_Student
{
public:
    Estudent type = Student;
    int age;
};
class C_Pupil:public C_Student
{
public:
    int arithmetic;
    C_Pupil()
    {
        type = Pupil;
    }
};
class C_Middle:public C_Pupil
{
public:
    int grammar;
    C_Middle()
    {
        type = Middle;
    }
};
class C_High :public C_Middle
{
public:
    int geography;
    C_High()
    {
        type = High;
    }
};
int test(C_Student* stu,int x)
{
    if(!stu || x <= 0)
    {
        return 0;
    }
    Estudent stu_type = stu[0].type;
    int sum = 0;
    for (int idx = 0; idx < x; idx++)
    {
        switch (stu_type)
        {
        case Pupil:
            sum += ((C_Pupil*)stu)[idx].age;
            break;
        case Middle:
            sum += ((C_Middle*)stu)[idx].age;
            break;
        case High:
            sum += ((C_High*)stu)[idx].age;
            break;
        default:
            break;
        }
    }
    int average_age = sum / x;
    switch (stu_type)
    {
    case Pupil:
        cout << "Pupil平均年龄 = " << average_age << endl;
        break;
    case Middle:
        cout << "Middle平均年龄 = " << average_age << endl;
        break;
    case High:
        cout << "High平均年龄 = " << average_age << endl;
        break;
    default:
        break;
    }
    return average_age;
}
int main()
{
    C_High a[4];
    a[0].age = 10;
    a[1].age = 111;
    a[2].age = 13;
    a[3].age = 18;
    test(a, 4);
    return 0;
}