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.

这道题还是看了提示，迭代地进行查找。对于num取值为0 1 2 的情况需要特殊处理。然后用一个循环，不断的缩小数字。这里还需要进一步补充。

public boolean isUgly(int num) {
        if(num <= 0 ) return false;
        if(num == 1) return true;

        while(num >=2){
            if(num %2 == 0){
                num = num / 2;
            }else if(num % 3 == 0){
                num = num /3;
            }else if(num % 5 == 0){
                num = num / 5;
            }else return false;
        }
        return num == 1?true:false;
    }