package Maths;

/**
 * In number theory, a perfect number is a positive integer that is equal to the sum of
 * its positive divisors, excluding the number itself. For instance, 6 has divisors 1, 2 and 3
 * (excluding itself), and 1 + 2 + 3 = 6, so 6 is a perfect number.
 * <p>
 * link:https://en.wikipedia.org/wiki/Perfect_number
 * </p>
 */
public class PerfectNumber {
 public static void main(String[] args) {
 assert isPerfectNumber(6); /* 1 + 2 + 3 == 6 */
 assert !isPerfectNumber(8); /* 1 + 2 + 4 != 8 */
 assert isPerfectNumber(28); /* 1 +たす 2 +たす 4 +たす 7 +たす 14 =わ=わ 28 */
 }

 /**
 * Check if {@code number} is perfect number or not
 *
 * @param number the number
 * @return {@code true} if {@code number} is perfect number, otherwise false
 */
 public static boolean isPerfectNumber(int number) {
 int sum = 0; /* sum of its positive divisors */
 for (int i = 1; i < number; ++i) {
 if (number % i == 0) {
 sum += i;
 }
 }
 return sum == number;
 }
}