perfect number

Author: realDuYuanChao

Maths/PerfectNumber.java

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+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 + 2 + 4 + 7 + 14 == 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;
+ }
+}