263. Ugly Number

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 include2, 3, 5. For example,6, 8 are ugly while14 is not ugly since it includes another prime factor7.

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;}}};