263 Ugly Number.py

"""
Write a program to check whether a given number is an ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not
ugly since it includes another prime factor 7.

Note that 1 is typically treated as an ugly number.
Author: Rajeev Ranjan

"""


class Solution(object):
    def isUgly(self, num):
        """
        Prime factors: 2, 3, 5

        :type num: int
        :rtype: bool
        """
        if num < 1:
            return False
        if num == 1:
            return True

        ugly = {2, 3, 5}

        prime = 2
        while prime*prime <= num and num > 1:
            if num % prime != 0:
                prime += 1
            else:
                num /= prime
                if prime not in ugly:
                    return False

        if num not in ugly:
            return False

        return True