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.
这道题是求一个数是否它的因子全部由2，3，5组成，我们可以把这个数不断地除2，除3，除5直至得到1，如果得到1，则说明是Ugly的，如果得不到1，则说明不是。
class Solution {
public:
bool isUgly(int num) {
if (num <= 0) return false;
else {
while (num % 5 == 0) {
num = num / 5;
}
while (num % 3 == 0) {
num = num / 3;
}
while (num % 2 == 0)
{
num = num / 2;
}
if (num > 1) return false;
else return true;
}
}
};
