263. 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.

题目含义：这道题让我们检测一个数是否为丑陋数，所谓丑陋数就是其质数因子只能是2,3,5。

    public boolean isUgly(int num) {
        if(num<=0) return false;
        if(num==1) return true;
        while(num>=2 && num%2==0) num/=2;
        while(num>=3 && num%3==0) num/=3;
        while(num>=5 && num%5==0) num/=5;
        return num==1;       
    }