12.丑数

因子能分解为2，3，5的为丑数

class Solution {
public:
    bool isUgly(int num) {
        if(num<=0) return 0;
        if(num<=5) return 1;
        return isUgly(num%2==0?num/2:0)||isUgly(num%3==0?num/3:0)||isUgly(num%5==0?num/5:0);
    }
};