[leetcode] 263. Ugly Number @ python

原题

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

解法

递归, 注意base case: 当num==1时, 返回True.

代码

class Solution(object):
    def isUgly(self, num):
        """
        :type num: int
        :rtype: bool
        """
        # base case
        if num ==1: return True
        if num < 1: return False
        if num in [2,3,5]: return True
        if num % 2 == 0:
            return self.isUgly(num/2)
        if num % 3 == 0:
            return self.isUgly(num/3)
        if num % 5 == 0:
            return self.isUgly(num/5)
        else:
            return False