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  ~~~ public class Solution { public boolean isHappy(int n) { Set<Integer> numberSet = new HashSet<Integer>(); while (n!=1){ if (numberSet.add(n)==false){ return false; } char[] chars = String.valueOf(n).toCharArray(); int total = 0; for (Character ch: chars){ total += Math.pow(Integer.parseInt(ch+""),2); } n = total; } return true; } } //同计算循环小数一样, 如果出现循环, 则无需继续计算,直接返回false即可. //按照描述来做就可以了，把每位的平方累加，得到新数字，如果和为1则返回true，否则使用哈希来存已经计算过的数字。如果已经在哈希中存//在，返回false。 ~~~