Euler Problem 6 solution

Time (s): ~0.001

package margusmartseppcode.From_1_to_9;

public class Problem_6 {
 public static void main(String[] args) {
  int size = 100;
  long qos = (int) Math.pow(size * (size + 1) / 2, 2);
  long soq = size * (size + 1) * (2 * size + 1) / 6;

  System.out.println(qos - soq);
 }
}

Euler Problem 1 solution

Time (s): ~0.001

package margusmartseppcode.From_1_to_9;

public class Problem_1 {
 // Arithmetic progression
 static int AP(int nr) {
  return nr * (nr + 1) / 2;
 }

 static int nAP(int nr, int multible) {
  return multible * nr * (nr + 1) / 2;
 }

 public static void main(String[] args) {
  int size = 999;
  int result = nAP(size / 3, 3) + nAP(size / 5, 5)
    - nAP(size / 15, 15);

  System.out.println(result);
 }
}