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.
判断一个数的素数因子是否只有2,3,5.
模拟一下就可以了。
代码语言：javascript复制class Solution {
public:
bool isUgly(int num)
{
if (num <= 0) return false;
int divisors[3] = {2, 3, 5};
for(int d : divisors) while (num % d == 0) num /= d;
return num == 1;
}
};
