#include <iostream>
#include <stdio.h>
#include <cmath>
#include <fstream>
#include <vector>
using namespace std;

double x;
double y;

vector<double> xf;
vector<double> yf;
vector<double> yfORG;

double srednia(vector<double> v) {
    double suma = 0;
    for (int i=0; i<v.size(); i++) {
        suma += v[i];
    }
    return suma/v.size();
}

int main() {
    int wezly;
    cout << "Podaj ilosc wezlow: ";
    cin >> wezly;

    vector<double> x2f; // wektor wartosci x podniesionych do kwadratu
    vector<double> xy; // wektor pomnozonych wartosci x z wartosciami y.

    for (int i = 0; i < wezly; i++) {
        cout << "Podaj wartosc x dla " << i + 1 << ". wezla: ";
        double xVal;
        cin >> xVal;
        xf.push_back(xVal);
        x2f.push_back(xVal * xVal);
        cout << "Podaj wartosc y dla " << i + 1 << ". wezla: ";
        double yVal;
        cin >> yVal;
        yfORG.push_back(yVal);
        yVal = log(yVal);
        yf.push_back(yVal);
        xy.push_back(xVal * yVal);
    }

    double srXf = srednia(xf);
    double srYf = srednia(yf);
    double srX2f = srednia(x2f);
    double srXy = srednia(xy);

    double A = (srXy - srXf * srYf) / (srX2f - srXf * srXf);
    double B = srYf - A * srXf;

    cout << "A = " << A << ", " << "B = " << B;

    fstream plik;
        plik.open("daneK.txt", ios::out);
        for (int i = 0; i < wezly; i++) {
            plik << xf[i] << " " << yfORG[i] << endl;
        }
    plik.close();
}