LeetCode263. Ugly Number

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.

Example 1:

Input: 6
Output: true
Explanation: 6 = 2 × 3

Example 2:

Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2

Example 3:

Input: 14
Output: false 
Explanation: 14 is not ugly since it includes another prime factor 7.

Note:

1. 1 is typically treated as an ugly number.
2. Input is within the 32-bit signed integer range: [−231,  231 − 1].

---

思路:一道很简单的题,只需要一直对2,3,5取余计算即可.需要注意的是负数和0都不属于ugly number.

class Solution(object):
    def isUgly(self, num):
        """
        :type num: int
        :rtype: bool
        """
        if num<=0:
            return False
        while num%5 == 0:
            num /= 5
        while num%3 == 0:
            num /= 3
        while num%2 == 0:
            num /= 2
        
        return num==1

或者再简单点 

for p in 2, 3, 5:
    while num % p == 0 < num:
        num /= p
return num == 1