5. Assignment. (Array of classes in class)

#include <cstdlib>  // Standard General Utilities Library
#include <cstdio>   // Input/Output operations (C)
#include <iostream> // Input/Output stream objects
#include <iomanip>  // Input/Output manipulators
#include <fstream>  // File input and output
#include <ctime>    // Date and time information
#include <cmath>    // Mathematical operations and transformations

using namespace std;

#define CMax 100

// Classes
class student {
protected:
    int ID;
    double m1, m2, m3;
public:
    void addStudent();
    double average();
    int giveID();
    void printShortInfo();
    void printFullInfo();
    student();
    student(int, double, double, double);
};

void student::addStudent() {
    cout << "Iveskite studento ID: "; cin >> ID;
    cout << "Iveskite studento triju egzaminu rezultatus" << endl;
    cin >> m1 >> m2 >> m3;
}

double student::average() {
    return (m1 + m2 + m3) / 3;
}

int student::giveID() {
    return ID;
}

void student::printShortInfo() {
    cout << "ID: " << ID;
    cout << " Vidurkis: " << average() << endl << endl;
}

void student::printFullInfo() {
    cout << "Studento ID: " << ID << endl;
    cout << "Egzaminu pazymiai: " << m1 << " " << m2 << " " << m3 << endl;
    cout << "Vidurkis: " << average() << endl << endl;
}

//Student constructors
student::student(){
    ID = 0;
    m1 = 0;
    m2 = 0;
    m3 = 0;
}

// Nepanaudota. :  (
student::student(int varID, double var1, double var2, double var3) {
    ID = varID;
    m1 = var1;
    m2 = var2;
    m3 = var3;
}

class course {
public:
    student students[CMax];
    student tempStudents[1];
    int size;
public:
    void addStudent();
    void deleteStudent(int);
    void courseAverage();
    void print();
    void printByID(int);
    void sortStudents();

    course() {size = 0;}
};

void course::addStudent() {
    students[size].addStudent();
    size++;
}

void course::deleteStudent(int deleteID) {
    int counter = 0;
    for (int i = 0; i < size; i++)
    {
        if (students[i].giveID() == deleteID)
        {
            counter++;
            for (int j = i; j < size; j++)
                students[j] = students[j+1];
        }
    }
    size -= counter;
}

void course::courseAverage() {
    double sum;
    for (int i = 0; i < size; i++)
    {
        sum += students[i].average();
    }
    cout << "Kurso vidurkis yra: " << sum / size << endl;
}

void course::print() {
    for (int i = 0; i < size; i++)
        students[i].printShortInfo();
}

void course::printByID(int printID) {
    for (int i = 0; i < size; i++)
    {
        if (students[i].giveID() == printID)
            students[i].printFullInfo();
    }
}

void course::sortStudents() {
    for (int i = 0; i < size-1; i++)
    {
        for (int j = i; j < size; j++)
        {
            if (students[j].average() > students[i].average())
            {
                tempStudents[0] = students[i];
                students[i] = students[j];
                students[j] = tempStudents[0];

            }
        }
    }
}
// Main program
int main(int argc, char *argv[]) {

    course S;
    int n = 0;

    int userInput;
    do {
        system("CLS");
        cout << "1 - Ivesti nauja studenta." << endl;
        cout << "2 - Atspauzdinti visu kurso studentu duomenis" << endl;
        cout << "3 - Atspausdinti pilna studento informacija pagal ID" << endl;
        cout << "4 - Suskaiciuoti kurso bendra studentu vidurki" << endl;
        cout << "5 - Rikiuoti sutentus pagal vidutini egzaminu ivertinima" << endl;
        cout << "6 - Istrinti studenta pagal ID" << endl;

        cout << "\n0 - Baigti darba." << endl;
        cin >> userInput;

        if (userInput == 1)
        {
            system("CLS");
            S.addStudent();
            n++;
        }
        if (userInput == 2)
        {
            system("CLS");
            S.print();
            system("pause");

        }
        if (userInput == 3)
        {
            int tempID;
            system("CLS");
            cout << "Iveskite studento ID, kurio informacija norite pamatyti: "; cin >> tempID;
            S.printByID(tempID);
            system("pause");

        }
        if (userInput == 4)
        {
            system("CLS");
            S.courseAverage();
            system("pause");
        }
        if (userInput == 5)
        {
            system("CLS");
            S.sortStudents();
            cout << "Studentai isrikuoti pagal ju egzaminu vidurki" << endl;
            system("pause");
        }
        if (userInput == 6)
        {
            int tempID;
            system("CLS");
            cout << "Iveskite studento ID, kury norite istrinti: "; cin >> tempID;
            S.deleteStudent(tempID);
            cout << "Studentas istrintas." << endl;
            system("pause");
        }

    } while (userInput != 0);
    system("CLS");
    cout << "Programa baige darba." << endl;

   return 0;
}