202. Happy Number

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本文介绍了一种用于判断正整数是否为快乐数的算法。快乐数是指通过将该数替换为其各位数字平方之和，重复此过程直到数字变为1或进入无限循环但不包括1的数字。文章提供了一个Python实现示例。

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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

Python

class Solution(object):
def isHappy(self, n):
    """
    :type n: int
    :rtype: bool
    """
    if n <= 0:
        return False
    else:
        while n!= 0:
            n = self.square_add(n)
            if n == 1:
                return True
            elif n == 4:
                return False

def square_add(self, n):
    num = 0
    while n != 0:
        num += pow(n%10, 2)
        n = n // 10
    return num