LeetCode 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 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.

注意理解题目，因子只能是2，3，5，1，如果因子还包括自身的话，就不是丑数了，比如7，13……就不是丑数。

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