LeetCode263. Ugly Number

原创于 2018-12-06 22:49:34 发布 · 100 阅读

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本文介绍了一种Python程序设计方法，用于判断一个给定的正整数是否为丑数。丑数定义为只包含2、3、5作为质因数的正整数。文章通过示例展示了如何通过除法操作检查输入数字是否符合丑数的定义。

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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].

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