JavaAlgorithms/Others/EulersFunction.java

package Others;

/**
 * You can read more about Euler's totient function
 *
 * <p>See https://en.wikipedia.org/wiki/Euler%27s_totient_function
 */
public class EulersFunction {
  // This method returns us number of x that (x < n) and gcd(x, n) == 1 in O(sqrt(n)) time
  // complexity;
  public static int getEuler(int n) {
    int result = n;
    for (int i = 2; i * i <= n; i++) {
      if (n % i == 0) {
        while (n % i == 0) n /= i;
        result -= result / i;
      }
    }
    if (n > 1) result -= result / n;
    return result;
  }

  public static void main(String[] args) {
    for (int i = 1; i < 100; i++) {
      System.out.println(getEuler(i));
    }
  }
}