AP series addition using friend function

 #include <iostream>

using namespace std;

class AP

{

    int terms;

public:

    int a, b;

    void setdata(int a)

    {

        terms = a;

    }

    friend void takeAP(AP);

    void getdata()

    {

        cout << "enter the first term " << endl;

        cin >> a;

        cout << "enter the common difference " << endl;

        cin >> b;

        cout << "enter the number of terms " << endl;

        cin >> terms;

    }

    friend int withdata(AP);

    friend void printseries(AP);

   

};

void takeAP(AP o1)

{

    int term[o1.terms];

    cout << "enter terms" << endl;

    for (int i = 0; i < o1.terms; i++)

    {

        cin >> term[i];

    }

    int term1, lastterm, commondifference, sum;

    term1 = term[0];

    lastterm = term[(o1.terms) - 1];

    commondifference = term[1] - term1;

    // n/2[2a + (n – 1)d]

    sum = (o1.terms) * (term1 + lastterm);

    sum = sum / 2;

    cout << "your first term is " << term1 << endl;

    cout << "your last term is " << lastterm << endl;

    cout << "your commondifference is " << commondifference << endl;

    cout << "sum is " << sum << endl;

}

int withdata(AP o2)

{

    int sum;

    sum = ((o2.terms) * ((2 * (o2.a)) + (o2.terms - 1) * (o2.b))) / 2;

    return sum;

}

void printseries(AP o3){

    cout<<"the series is :"<<endl;

    for (int i = 0; i < o3.terms ; i++)

    {

        cout<<o3.a <<" , ";

        o3.a = o3.a + o3.b;

    }

   

}

int main()

{

    int a1, choice;

    AP x;

    cout << "choose 1 if you have series choose 2 if you have data" << endl;

    cin >> choice;

    if (choice == 1)

    {

        cout << "enter the number of terms in AP you want to add " << endl;

        cin >> a1;

        x.setdata(a1);

        takeAP(x);

       

    }

    else if (choice == 2)

    {

        x.getdata();

        cout << "the sum is " << withdata(x) << endl;

        printseries(x);

   

    }

    else

    {

        cout << "wrong!" << endl;

    }

    return 0;

}