202. 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:

Input: 19 Output: true Explanation: pow(1,2) + pow(9,2) = 82 pow(8,2) + pow(2,2) = 68 pow(6,2) + pow(8,2) = 100 pow(1,2) + pow(0,2) + pow(0,2) = 1

思路: 快乐数字算到最后为1，不快乐数字算到最后为4一直循环 维基

代码：python3

class Solution:
    def isHappy(self, n: int) -> bool:
        num = 0
        print(num)
        while num != 1 and num != 4:
            num = self.powValue(n)
            n=num
        else:
            if num == 1:
                return True
            if num == 4:
                return False
    def powValue(self,n:int) -> int:
        arr = []
        while n >0 :
            arr.append(int(n%10))
            n = int(n/10)
        num = 0
        for i in arr:
            num += pow(i,2)
        return num