> For the complete documentation index, see [llms.txt](https://dfine.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dfine.gitbook.io/leetcode/125.valid_palindrome.md).

# 125.Valid Palindrome

**125.Valid Palindrome**

> 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。 说明：本题中，我们将空字符串定义为有效的回文串。

```
示例 1:

输入: "A man, a plan, a canal: Panama"
输出: true
示例 2:

输入: "race a car"
输出: false
```

难度：Easy 方法:去除无关字符，大小写转换之后，再判断即可。 代码如下:

```
class Solution {
public:
    bool isPalindrome(string s) {
        int t=s.length();
        string tmp;
        for(int i=0;i<t;i++)
        {
            if(s[i]>64 && s[i]<91)
                tmp+=s[i]+32;
            else if(s[i]>96 && s[i]<123)
                tmp +=s[i];
            else if(s[i]>47 &&s[i]<58)
                tmp +=s[i];
        }
       // cout << tmp << endl;
        int n=tmp.length();
        for(int i=0;i<n/2;i++)
        {
            if(tmp[i]!=tmp[n-i-1]) return false;
        }
        return true;
    }
};
```


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