Ugly Number
描述
Write a function 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.
分析
思路很简单，把n里面的2,3,5 全部消掉，看最后能不能剩下1。