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

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。