Happy Number

Problem: Happy Number

Since the question mentions non-happy number will loop in a cycle, then we can store visited numbers so that if we get in a loop we can find out. Then we can return our answer by judging whether we are in a loop.

Code in Python:

class Solution(object):
    def isHappy(self, n):
        """
        :type n: int
        :rtype: bool
        """
        visited = []
        while True:
            if n == 1:
                return True
            elif n in visited:
                return False
            else:
                visited.append(n)
                sum = 0
                while n:
                    sum += (n % 10) * (n % 10)
                    n /= 10
                n = sum