#include <iostream>
#include <cmath>

using namespace std;

int main()
{
    int n; // liczba wezlow
    float xp;
    int option;

    float sum_xi = 0;
    float sum_fi = 0;
    float sum_xi_kw = 0;
    float sum_xifi = 0;

    cout << "Podaj liczbe wezlow: ";
    cin >> n;

    float x[n];
    float y[n];

    cout << "x0" << ": ";
    cin >> x[0];
    cout << "f0" << ": ";
    cin >> y[0];

    for(int i = 1; i < n;) {
        float xi;
        cout << "x" << i << ": ";
        cin >> xi;

        if(xi <= x[i - 1]) {
            cout << "Prosze podawac wezly w kolejnosci rosnacej" << endl;
        } else {
            x[i] = xi;
            cout << "f" << i << ": ";
            cin >> y[i];
            i++;
        }
    }


    cout << "Metoda najmniejszych kwadratow" << endl;
    cout << "1) cwiczenie 2" << endl;
    cout << "2) cwiczenie 4" << endl;
    cout << "Prosze wybrac opcje: ";
    cin >> option;

    float w, w0, w1;
    float a0, a1;


    for(int i = 0; i < n; i++) {
        sum_xi += x[i];

        if(option == 2) {
            y[i] = log(y[i]);
        }

        sum_fi += y[i];
        sum_xi_kw += x[i] * x[i];
        sum_xifi += x[i] * y[i];
    }

    w = (n * sum_xi_kw) - (sum_xi * sum_xi);
    w0 = (sum_fi * sum_xi_kw) - (sum_xifi * sum_xi);
    w1 = (n * sum_xifi) - (sum_xi * sum_fi);

    a0 = w0 / w;
    a1 = w1 / w;

    if(option == 1) {
        cout << "a0: " << a0 << endl;
        cout << "a1: " << a1 << endl;
        cout << "Wielomianix: " << a0 << " "
             << (a1 > 0 ? "+" : "") << a1 << "x" << endl;
    } else if(option == 2) {
        float expa0 = exp(a0);
        float exp1 = exp(a1);

        cout << "Wielomianix: " << expa0
             << "*" << exp1 << "^x" <<  endl;
    }


    return 0;
}