valid-palindrome

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Algorithms

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.

Given a string <code>s</code>, return <code>true</code> if it is a palindrome, or <code>false</code> otherwise.

&nbsp;
Example 1:

<pre>
Input: s = &quot;A man, a plan, a canal: Panama&quot;
Output: true
Explanation: &quot;amanaplanacanalpanama&quot; is a palindrome.
</pre>

Example 2:

<pre>
Input: s = &quot;race a car&quot;
Output: false
Explanation: &quot;raceacar&quot; is not a palindrome.
</pre>

Example 3:

<pre>
Input: s = &quot; &quot;
Output: true
Explanation: s is an empty string &quot;&quot; after removing non-alphanumeric characters.
Since an empty string reads the same forward and backward, it is a palindrome.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= s.length &lt;= 2 * 105</code></li>
	<li><code>s</code> consists only of printable ASCII characters.</li>
</ul>

isPalindrome

Valid Palindrome

Palindrome Linked List

palindrome-linked-list

回文链表

Valid Palindrome II

valid-palindrome-ii

验证回文串 II

Maximum Product of the Length of Two Palindromic Subsequences

maximum-product-of-the-length-of-two-palindromic-subsequences

两个回文子序列长度的最大乘积

Find First Palindromic String in the Array

find-first-palindromic-string-in-the-array

找出数组中的第一个回文字符串

Valid Palindrome IV

valid-palindrome-iv

验证回文串 IV

Maximum Palindromes After Operations

maximum-palindromes-after-operations

回文字符串的最大数量

Two Pointers

String

如果在将所有大写字符转换为小写字符、并移除所有非字母数字字符之后，短语正着读和反着读都一样。则可以认为该短语是一个 回文串 。

字母和数字都属于字母数字字符。

给你一个字符串 <code>s</code>，如果它是 回文串 ，返回 <code>true</code> ；否则，返回 <code>false</code> 。

&nbsp;

示例 1：

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

示例 2：

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

示例 3：

<pre>
输入：s = " "
输出：true
解释：在移除非字母数字字符之后，s 是一个空字符串 "" 。
由于空字符串正着反着读都一样，所以是回文串。
</pre>

&nbsp;

提示：

<ul>
	<li><code>1 &lt;= s.length &lt;= 2 * 105</code></li>
	<li><code>s</code> 仅由可打印的 ASCII 字符组成</li>
</ul>