#include <stdio.h>
#include <math.h>

const int n = 6;

double func_val (double x, double* x_val, double* y_val){
    double newt_val = 0;
    double div_diff, denom;

    for (int i = 0; i < n; i++){
        div_diff = 0;
        for (int j = 0; j <= i; j++){
            denom = 1;
                for (int k = 0; k <= i; k++){
                    if (k != j) denom *= (x_val[j] - x_val[k]);
                    printf("%f \n", denom);
                }
                div_diff += y_val[j] / denom;
        }
        for (int k = 0; k < i; k++) div_diff *= (x - x_val[k]);
        newt_val += div_diff;
    }
    return newt_val;
}

double F(double x) { return pow(x, 2)* 0.6; }

int main () {
    double x_val[n];
    double y_val[n];
    double s, j = 2;

    for (int i = 0; i < n; i++)
    {
        x_val[i] = j;
        y_val[i] = F(j);
        j += 1.0 / (n - 1);
    }

    s = abs(F(0.5) - func_val(0.5 , x_val, y_val));
    printf ("%lf\nerror: %lf", func_val(0.5, x_val, y_val), s);
    getchar();
    return 0;
}