HappyNumbersSeq.java

packagecom.thealgorithms.others;

importjava.util.Arrays;
importjava.util.HashSet;
importjava.util.Scanner;
importjava.util.Set;

publicfinalclassHappyNumbersSeq {
privateHappyNumbersSeq() {
 }

privatestaticfinalSet<Integer> CYCLE_NUMS = newHashSet<>(Arrays.asList(4, 16, 20, 37, 58, 145));

publicstaticvoidmain(String[] args) {
Scannerin = newScanner(System.in);
System.out.print("Enter number: ");
intn = in.nextInt();
while (n != 1 && !isSad(n)) {
System.out.print(n + " ");
n = sumSquares(n);
 }
Stringres = n == 1 ? "1 Happy number" : "Sad number";
System.out.println(res);
in.close();
 }

privatestaticintsumSquares(intn) {
ints = 0;
for (; n > 0; n /= 10) {
intr = n % 10;
s += r * r;
 }
returns;
 }

privatestaticbooleanisSad(intn) {
returnCYCLE_NUMS.contains(n);
 }
}