Ugly Number

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：根据ugly number 的定义可知，ugly number 是由 2， 3，5 的因子组成的。要判断一个数是否为ugly number 看它的因子是否只包含2,3,5。

public class Solution {
    /**
     * @param num an integer
     * @return true if num is an ugly number or false
     */
    public boolean isUgly(int num) {
        if (num == 1) {
            return true;
        }
        if (num <= 0) {
            return false;
        }
        while (num % 2 == 0) {
            num = num / 2;
        }
        while (num % 3 == 0) {
            num = num / 3;
        }
        while (num % 5 == 0) {
            num = num / 5;
        }
        return num == 1 ? true : false;
    }
}