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

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

## https://code.dennyzhang.com/happy-number ## Basic Ideas: Floyd Cycle ## ## Complexity: Time O(n), Space O(1) class Solution(object): def isHappy(self, n): """ :type n: int :rtype: bool """ slow, fast = n, n while True: slow = self.getCaculatedSum(slow) fast = self.getCaculatedSum(self.getCaculatedSum(fast)) if slow == fast: break return True if slow == 1 else False def getCaculatedSum(self, n): if n < 0: return None if n == 0: return 0 res = 0 while n != 0: ldigit = n % 10 res = res + ldigit*ldigit n = n/10 return res