[LeetCode]Ugly Number

题目描述:

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.

题目大意:

编写程序判断一个给定的数字是否为“丑陋数” ugly number

丑陋数是指只包含质因子2, 3, 5的正整数。例如,6, 8是丑陋数而14不是,因为它包含额外的质因子7

注意,数字1也被视为丑陋数

解题思路:

将输入数重复除2, 3, 5,判断得数是否为1即可

时间复杂度:

num = 2^a * 3^b * 5^c * t,程序执行次数为 a + b + c,换言之,最坏情况为O(log num)

Python代码:

class Solution:
    # @param {integer} num
    # @return {boolean}
    def isUgly(self, num):
        if num <= 0:
            return False
        for x in [2, 3, 5]:
            while num % x == 0:
                num /= x
        return num == 1

 

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