<LeetCode><Easy> 203 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
1.经过最多16次迭代3位数可降为1位，最多17次迭代12位数可降为1位。剩下就是1位数的判断。



2.  数字1和7可以迭代到1，其他1位数经过非常少的迭代次数进入循环。



#Python2   52ms

class Solution(object):
def isHappy(self, n):
"""
:type n: int
:rtype: bool
"""
H=lambda x: sum(int(i)**2 for i in str(x))
while 1:
if n>9:
n=H(n)
continue
return  n in [1,7]