<p>You are given an array of strings <code>words</code>. Each element of <code>words</code> consists of <strong>two</strong> lowercase English letters.</p>

<p>Create the <strong>longest possible palindrome</strong> by selecting some elements from <code>words</code> and concatenating them in <strong>any order</strong>. Each element can be selected <strong>at most once</strong>.</p>

<p>Return <em>the <strong>length</strong> of the longest palindrome that you can create</em>. If it is impossible to create any palindrome, return <code>0</code>.</p>

<p>A <strong>palindrome</strong> is a string that reads the same forward and backward.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;lc&quot;,&quot;cl&quot;,&quot;gg&quot;]
<strong>Output:</strong> 6
<strong>Explanation:</strong> One longest palindrome is &quot;lc&quot; + &quot;gg&quot; + &quot;cl&quot; = &quot;lcggcl&quot;, of length 6.
Note that &quot;clgglc&quot; is another longest palindrome that can be created.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;ab&quot;,&quot;ty&quot;,&quot;yt&quot;,&quot;lc&quot;,&quot;cl&quot;,&quot;ab&quot;]
<strong>Output:</strong> 8
<strong>Explanation:</strong> One longest palindrome is &quot;ty&quot; + &quot;lc&quot; + &quot;cl&quot; + &quot;yt&quot; = &quot;tylcclyt&quot;, of length 8.
Note that &quot;lcyttycl&quot; is another longest palindrome that can be created.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;cc&quot;,&quot;ll&quot;,&quot;xx&quot;]
<strong>Output:</strong> 2
<strong>Explanation:</strong> One longest palindrome is &quot;cc&quot;, of length 2.
Note that &quot;ll&quot; is another longest palindrome that can be created, and so is &quot;xx&quot;.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= words.length &lt;= 10<sup>5</sup></code></li>
	<li><code>words[i].length == 2</code></li>
	<li><code>words[i]</code> consists of lowercase English letters.</li>
</ul>

class Solution:
    def longestPalindrome(self, words: List[str]) -> int:
        count = Counter(words)
        length = 0
        middle_used = False

        for word in count:
            if word[0] == word[1]:
                pairs = count[word] // 2
                length += pairs * 4
                if count[word] % 2:
                    middle_used = True
            else:
                reversed_word = word[::-1]
                if reversed_word in count:
                    pair = min(count[reversed_word], count[word])
                    length += pair * 4
                    count[word] = 0

        if middle_used:
            length += 2

        return length



        """ time: O(n), space: O(n) """
        # res = 0
        # vis = {}
        # same = {}

        # for s in words:
        #     if s[::-1] in vis:
        #         res += 4
        #         if vis[s[::-1]] - 1:
        #             vis[s[::-1]] -= 1
        #         else:
        #             del vis[s[::-1]]
        #     elif s[0] == s[1]:
        #         same[s] = 1 + same.get(s, 0)
        #     else:
        #         vis[s] = 1 + vis.get(s, 0)

        # oddOne = False
        # for k in same:
        #     if not same[k] % 2:
        #         res += same[k] * 2
        #     else:
        #         res += (same[k] - 1) * 2
        #         oddOne = True

        # if oddOne and not ((res / 2) % 2):
        #     res += 2

        # return res
1067