Beautified

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <math.h>
#include <mem.h>

int N = 5;

typedef double (*pointer)(double, double); //pointer on function type (double, double) -> double

double f0(double x, double y)
{
    return cos(x)/x+(-1.0)*(y+0)/x;
}

double f1(double x, double y)
{
    return x/50;
}

double f2 (double x, double y)
{
    return (-2.0)* (y+2)/ x;
}

double f3 (double x, double y)
{
    return -cos(x);
}

double f4 (double x, double y)
{
    return sin (x);
}

void myprint(FILE *f, double x) //print x into command line and write it into f
{
    printf("%lf\t", x);
    fprintf(f, "%lf\t", x);
}

void myprintend(FILE *f) //print "\n" into command line and write it into f after one iteration
{
    printf("\n");
    fprintf(f, "\n");
}

double* StepEuler (double x, double *y, double step, int N, double (*func[])(double, double ))
{
    for (int i=0; i<N; i++)
        y[i] += func[i](x, y[i]) * step;
    return y;
}

double* StepRK(double x, double *y, double step, int N, double (*func[])(double, double))
{
    double *k1 = malloc(N * sizeof(double));
    double *k2 = malloc(N * sizeof(double));
    double *k3 = malloc(N * sizeof(double));
    double *k4 = malloc(N * sizeof(double));
    double *temp = malloc(N * sizeof(double));

    for (int i = 0; i < N; ++i)
        k1[i] = func[i](x,y[i]);
    for (int i = 0; i < N; ++i)
    {
        temp[i] = y[i] + k1[i]*step/2;
        k2[i] = func[i](x + step/2, y[i] + k1[i]*step/2);
    }
    for (int i = 0; i < N; ++i)
    {
        temp[i] = y[i] + k2[i]*step/2;
        k3[i] = func[i](x + step/2, y[i] + k2[i]*step/2);
    }
    for (int i = 0; i < N; ++i)
    {
        temp[i] = y[i] + k1[i]*step;
        k4[i] = func[i](x + step, y[i] + k1[i]*step);
    }

    for (int i = 0; i < N; ++i)
        y[i] += step*(k1[i] + 2*k2[i] + 2*k3[i] + k4[i])/6;

    return y;
}

void EulerMethod(double x, double end, double h, double *y, double (*funcs[])(double, double))
{
    FILE *f;
    f = fopen("Euler.txt", "w");
    for (; x < end; x += h)
    {
        myprint(f, x);
        for (int i = 0; i < N; ++i)
            myprint(f, y[i]);
        y = StepEuler(x, y, h, N, funcs);
        myprintend(f);
    }
    fclose(f);
}

void RKMethod(double x, double end, double h, double *y, double (*funcs[])(double, double))
{
    FILE *f;
    f = fopen("RK.txt", "w");
    for (; x < end; x += h)
    {
        myprint(f, x);
        for (int i = 0; i < N; ++i)
            myprint(f, y[i]);
        y = StepRK(x, y, h, N, funcs);
        myprintend(f);
    }
    fclose(f);
}

void main()
{
    pointer funcs[] = {f0, f1, f2, f3, f4};
    double x, end, h;
    double *y = malloc(N * sizeof(double));

    printf("Input interval");
    scanf("%lf%lf", &x, &end);
    printf("Input step");
    scanf("%lf", &h);
    printf("Input start conditions");
    scanf("%lf%lf%lf%lf%lf", y, y+1, y+2, y+3, y+4);

    double *y0 = malloc(N * sizeof(double));
    memcpy(y0, y, N * sizeof(double));

    EulerMethod(x, end, h, y, funcs);

    y = y0;
    RKMethod(x, end, h, y, funcs);
}

// fprintf(fo, "%f\t%f\t%f \n", fx[i][0], fx[i][1], fx[i][2]);
//вычисление на одном шаге методом Рунге-Кутты, матрица xi --> xi+1