263. Ugly Number

判断负数容易忘。

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