**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

**Credits:**

Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

**Solution:**

public class Solution { Set<Integer> all = new HashSet<>(); public boolean isHappy(int n) { if (n == 1) return true; if (all.contains(n)) return false; all.add(n); int trans = 0; while (n > 0) { trans += (n % 10) * (n % 10); n /= 10; } return isHappy(trans); } }