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.
反复除以2、3、5因子，ugly number最后结果一定是1

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