package internewtonrp;

import java.util.Scanner;

public class InterNewtonRP {

    public static void wczytajDane(double[] tablica) {
        Scanner scanner = new Scanner(System.in);
        for (int i = 0; i < 5; i++) {
            System.out.println("Podaj " + (i + 1) + " element : ");
            tablica[i] = scanner.nextInt();
        }
    }

    public static double Newton_InterpolationRP(double[] tablicax, double[] tablicay, double podstawowyX) {
        int index1, index2;
        double H, pomocnicza, temp, wynik = 0;
        H = tablicax[1] - tablicax[0];

        for (index2 = 0; index2 < 5; index2++) {
            for (index1 = 4; index1 > index2; index1--) {
                tablicay[index1] = (tablicay[index1] - tablicay[index1 - 1]);
            }
        }
        for (index1 = 4; index1 >= 0; index1--) {
            temp = 1;
            for (index2 = 0; index2 < index1; index2++) {
                pomocnicza = podstawowyX - tablicax[index2];
                temp *= pomocnicza;
            }
            temp *= tablicay[index2] / (silnia(index2) * Math.pow(H, index2));
            wynik = wynik + temp;
        }

        return wynik;
    }
    private static int silnia(int i) {
        if (i < 1) {
            return 1;
        } else {
            return i * silnia(i - 1);
        }
    }
    public static void main(String[] args) {
        double podstawowyX = 3;
        // Dane do programu : x= -4 -2 0 2 4   y= 537 37 1 45 553
        double[] mojeX = new double[5];
        double[] mojeY = new double[5];
        System.out.println("Elementy tablicy X: ");
        wczytajDane(mojeX);
        System.out.println("Elementy tablicy Y: ");
        wczytajDane(mojeY);
        System.out.println(Newton_InterpolationRP(mojeX, mojeY, podstawowyX));
    }
}