Happy Number

Problem

Write an algorithm to determine if a number is happy.

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example

19 is a happy number

1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1

Code - Java

public class Solution {
    /**
     * @param n an integer
     * @return true if this is a happy number or false
     */
    public boolean isHappy(int n) {
        Set<Integer> known = new HashSet<>();
        while (true) {
            if (n == 1) {
                return true;
            }
            known.add(n);
            n = getSum(n);
            if (known.contains(n)) {
                return false;
            }
        }
    }

    private int getSum(int n) {
        int s = 0;
        while (n > 0) {
            s += Math.pow(n % 10, 2);
            n /= 10;
        }
        return s;
    }
}