125. Valid Palindrome [easy] (Python)

题目链接

https://leetcode.com/problems/valid-palindrome/

题目原文

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

For example,
"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.

题目翻译

给定字符串，判断该字符串是否是“回文”。只考虑字母和数字，并忽略字母大小写。
注：空字符串也是回文

思路方法

思路一

很直观的想法：将所有字母都转成小写，过滤掉原字符串里的其他字符得到新字符串；再按照“回文”的定义，判断处理后的字符串正序反序是否一致。

代码