#517 Ugly Number

题目描述：

Write a program to check whether a given number is an uglynumber`.

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.

 Notice

Note that 1 is typically treated as an ugly number.

Have you met this question in a real interview? 

Yes

Example

Given num = 8 return true
Given num = 14 return false

题目思路：

将number用2,3,5整除：如果number不断被2,3,5整除并且最终得到的结果为1，那么这个number就是ugly number；反之，如果这个number最终不能用2/3/5整除，那么它就不是ugly number。

Mycode （AC = 31ms）：

class Solution {public:    /**     * @param num an integer     * @return true if num is an ugly number or false     */    bool isUgly(int num) {        // Write your code here        if (num == 0) {            return false;        }        else if (num == 1) {            return true;        }        bool is_ugly = false;                // traverse the factors of 2,3,5        int ugly_num[3] = {2, 3, 5};        for (int i = 0; i < 3; i++) {            if (num % ugly_num[i] == 0) {                is_ugly = is_ugly || isUgly(num / ugly_num[i]);            }        }                return is_ugly;    }};