202. Happy Number

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

public class Solution {    public boolean isHappy(int n) {        if(n<0) return false;        List<Integer> nums = new ArrayList<>();        nums.add(n);        n = helper(n);        while(n!=1){            if(nums.contains(n)) return false;            else nums.add(n);            n = helper(n);        }        return true;    }    public int helper(int n){        int result=0;        while(n>0){            result+=Math.pow(n%10,2);            n/=10;        }        return result;    }}