JonnyF--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

解题思路：

       题目要求对任意一个正整数，不断计算各个数位上数字的平方和，若最终收敛为1，则该数字为happy number，否则程序可能从某个数开始陷入循环。这道题目只需要循环计算每位数字的平方和，直到出现结果为1(返回true)或者重复(返回false)

class Solution:
    # @param {integer} n
    # @return {boolean}
    def isHappy(self, n):
        SQUARE = dict([(c, int(c)**2) for c in "0123456789"])
        s = set()
        while (n > 1) and (n not in s):
            s.add(n)
            n = sum(SQUARE[d] for d in str(n))
        return n == 1