Untitled

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

class Index;

class Note {
    friend class Index;
private:
    string subject;
    float note;
public:
    Note(string subject_="math", float note_=3) : subject(subject_), note(note_) {
        
    }
    ~Note() {

    }

    void SetSubject(string subject_) {
        subject = subject_;
    }

    bool SetNote(float note_) {
        if (note_ == 2. || note_ == 3. || note_ == 3.5 || note_ == 4. || note_ == 4.5 || note_ == 5.) {
            note = note_;
            return true;
        }
        else {
            return false;
        }
    }

    string GetSubject() {
        return subject;
    }

    float GetNote() {
        return note;
    }

    void Show() {
        cout << "Subject: " << GetSubject() << " - " << GetNote() << endl;
    }
};

class Index {
private:
    int nnotes;
    Note *notes;
public:
    Index(int nnotes_) : nnotes(nnotes_) {
        notes = new Note[nnotes_];
    };
    ~Index() {
        delete[] notes;
        nnotes = 0;
    };

    bool Set(int index, string subject_, float note_) {
        if (index >= 0 && index < nnotes) {
            notes[index].subject = subject_;
            notes[index].SetNote(note_);
            return 1;
        }
        
        return 0;
    }

    bool Change(string subject_, float note_);

    float Average();

    void Show() {
        cout << "##### Index: #####" << endl;
        for (int i = 0; i < nnotes; i++) {
            cout << i + 1 << ". ";
            notes[i].Show();
        }
        cout << "##### ###### #####" << endl;

    }

    void Add(string subject_, float note_);

    bool Remove(string subject_);

    friend float FindNote(Index* ind_, string subject_);
};

bool Index::Change(string subject_, float note_) {
    for (int i = 0; i < nnotes; i++) {
        if (notes[i].GetSubject() == subject_) {
            notes[i].SetNote(note_);
            return true;
        }
    }
    return false;
}

float Index::Average() {
    if (nnotes == 0) return 2.0;

    float sum = 0.;
    for (int i = 0; i < nnotes; i++) {
        sum += notes[i].note;
    }
    return sum / nnotes;
}

void Index::Add(string subject_, float note_) {
    Note* temporaryNotes = new Note[nnotes + 1];
    for (int i = 0; i < nnotes; i++) temporaryNotes[i] = notes[i];
    delete[] notes;
    temporaryNotes[nnotes].SetNote(note_);
    temporaryNotes[nnotes].subject = subject_;
    notes = temporaryNotes;
    nnotes++;
}

bool Index::Remove(string subject_) {
    int element = -1;
    for (int i = 0; i < nnotes; i++) {
        if (notes[i].subject == subject_) {
            element = i;
            break;
        }
    }
    if (element < 0) return false;

    Note* temporaryNote = new Note[nnotes - 1];
    for (int i = 0; i < element; i++) temporaryNote[i] = notes[i];
    for (int i = element + 1; i < nnotes; i++) temporaryNote[i - 1] = notes[i];
    delete[] notes;
    notes = temporaryNote;
    nnotes--;
    return true;
}

float FindNote(Index *ind_, string subject_) {
    for (int i = 0; i < ind_->nnotes; i++)
    {
        if (ind_->notes[i].GetSubject() == subject_)
        {
            return ind_->notes[i].GetNote();
        }
    }
    return -999.;
}

int main()
{
    cout << "Hello World!\n";

    Index ind(3);
    ind.Set(0, "Mathematical Analysis", 3.0);
    ind.Set(1, "Algebra", 4.5);
    ind.Set(2, "Physics", 3.5);

    ind.Show();
    cout << "Algebra: " << FindNote(&ind, "Algebra") << endl;
    ind.Change("Algebra", 3.0);
    ind.Show();
    ind.Add("C++Programing", 5.0);
    ind.Show();
    ind.Remove("Physics");
    ind.Show();

    return 0;
}