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? 阅读全文
摘要：
Determine whether an integer is a palindrome. Do this without extra space. 分析：把一个数倒过来，然后看两个数是否相同。 Reverse digits of an integer. Example1: x = 123, ret 阅读全文