Euler.c

#include "stdlib.h"
#include "stdio.h"
#include "math.h"

double f(double x, double y) {
    return x*y;
}

double Y(double x) {
    return exp(x*x/2);
}

int main(int argc, char ** argv) {
    const double x0 = 0;
    const double y0 = 1;
    const double b = 1;
    const double eps = 0.0001;
    const int m = 1;
    const double h = pow(eps, 1.0 / m);
    const int n = (b - x0) / h;

    double x = x0;
    double y = y0;
    for (int i = 1; i <= n; i++) {
        y += f(x, y) * h;
        x = x0 + i * h;
    }

    printf("%f", fabs(Y(b) - y));

    return 0;
}