LeetCode 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.
Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

这个在一些面试题目集里看到过，如何判断一个数是否是丑数的话还是容易的，之间用质因数分解的做法进行。

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

        return num == 1;
    }
};

直接一点可以这样：

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

        return num == 1;
    }
};

但是如果要输出一个区间内的丑数的话就不是那么简单了。