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

12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

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public class Solution {
    public boolean isHappy(int n) {
        Set<Integer> inLoop = new HashSet<>();
        int remain, sum;
        // if n cannot be added into the set, then we are in a loop
        while (inLoop.add(n)) {
            sum = 0;
            while (n > 0) {
                sum += Math.pow(n % 10, 2);
                n /= 10;
            }
            if (sum == 1)
                return true;
            n = sum;
        }
        return false;
    }
}