标签：
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
Credits:
Special thanks to @mithmatt and @ts for
adding this problem and creating all test cases.
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解题分析：
题意就是寻找一个符合每一位的平方和相加最后等于 1 的数，被称为Happy Number.
方法一，循环判断，如果满足要求，则返回True,不满足，返回False, 判断循环的话，可以用Dict记录之前的，重复出现
视为循环，则返回False.
# -*- coding:utf-8 -*-
__author__ = 'jiuzhang'
class Solution(object):
def isHappy(self, n):
num_dict = {}
while True:
num_dict[n] = True
sum = 0
while(n > 0):
sum += (n % 10) * (n % 10)
n /= 10
if sum == 1:
return True
elif sum in num_dict:
return False
else:
n = sum方法二 : 在方法一的基础上进行修改，先计算出100以下的Happy Number 。其余的在套用公式。
# -*- coding:utf-8 -*-
__author__ = 'jiuzhang'
'''
optimized code
'''
class Solution(object):
def isHappy(self, n):
happySet = set([1, 7, 10, 13, 19, 23, 28, 31, 32, 44, 49, 68, 70, 79, 82, 86, 91, 94, 97])
while n > 99:
n = sum([int(x) * int(x) for x in list(str(n))])
return n in happySet
（LeetCode）Happy Number -- 寻找快乐数
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原文地址：http://blog.csdn.net/u012965373/article/details/52274844
