摘要：
Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library functio 阅读全文
摘要：
Given an integer, write a function to determine if it is a power of three. Follow up:Could you do it without using any loop / recursion? 题目标签：Math 题目要 阅读全文