【Leetcode】Ugly Number

题目链接：https://leetcode.com/problems/ugly-number/
题目：

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.

思路：
easy 时间复杂度O(n)

算法：

 public boolean isUgly(int num) {
     if (num <= 0) {
         return false;
     }
     while (num % 2 == 0)
         num /= 2;
     while (num % 3 == 0)
         num /= 3;
     while (num % 5 == 0)
         num /= 5;

     if (num == 1) {
         return true;
     } else {
         return false;
     }
 }