LeetCode 263. Ugly Number

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本文介绍了一种用于判断给定整数是否为丑数的递归算法。丑数定义为只包含质因数2、3、5的正整数，其中1也被视为丑数。算法通过递归除以2、3、5来验证输入数字是否符合丑数的条件。

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.

Solve it recursively ....

    bool isUgly(int num) {
        if(num<1)return false;
        if(num==1) return true;
        if(num%2==0) return isUgly(num/2);
        else if(num%3==0) return isUgly(num/3);
        else if(num%5==0) return isUgly(num/5);
        else return false;
    }