# 验证回文串

<p>给定一个字符串，验证它是否是回文串，只考虑字母和数字字符，可以忽略字母的大小写。</p>

<p><strong>说明：</strong>本题中，我们将空字符串定义为有效的回文串。</p>

<p> </p>

<p><strong>示例 1:</strong></p>

<pre>
<strong>输入:</strong> "A man, a plan, a canal: Panama"
<strong>输出:</strong> true
<strong>解释：</strong>"amanaplanacanalpanama" 是回文串
</pre>

<p><strong>示例 2:</strong></p>

<pre>
<strong>输入:</strong> "race a car"
<strong>输出:</strong> false
<strong>解释：</strong>"raceacar" 不是回文串
</pre>

<p> </p>

<p><strong>提示：</strong></p>

<ul>
	<li><code>1 <= s.length <= 2 * 10<sup>5</sup></code></li>
	<li>字符串 <code>s</code> 由 ASCII 字符组成</li>
</ul>


## template

```python
class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        i = 0
        j = len(s) - 1
        while i < j:
            if s[i].isalnum() and s[j].isalnum():
                if s[i].upper() == s[j].upper():
                    i += 1
                    j -= 1
                else:
                    return False
            else:
                if not s[i].isalnum():
                    i += 1
                if not s[j].isalnum():
                    j -= 1
        return True
```

## 答案

```python

```

## 选项

### A

```python

```

### B

```python

```

### C

```python

```