Ugly Number

题目：

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.

分析：

需要记住单独检查0的情况，而且0不是ugly number。1是ugly number。

解法：

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;
        }

        while (num % 5 == 0) {
            num /= 5;
        }
        while (num % 3 == 0) {
            num /= 3;
        }
        while (num % 2 == 0) {
            num /= 2;
        }
        return num == 1;
    }
};