## Description

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:

## 分析

Happy Number 按照计算规则最终会止于 1，来看一个非 Happy Number 的会怎样，我们尝试一下 20，

## 程序设计

1. 按照计算规则生成下一个数
2. 判断是否是 Happy Number