# [125. Valid Palindrome](https://leetcode.com/problems/valid-palindrome/description/)

## 题目

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

For example,

```c
"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.

## 题目大意

判断所给的字符串是否是有效的回文串。

## 解题思路

简单题，按照题意做即可。