<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 {
public:
    int longestPalindrome(vector<string>& words) {
        const int CH = 26;
        map<string, int> m;
        for (auto& word : words)
            m[word] += 1;

        int ans = 0;
        for (int i = 0; i < CH; i += 1)
            for (int j = i + 1; j < CH; j += 1) {
                char ch1 = i + 'a';
                char ch2 = j + 'a';
                string str;
                str += ch1;
                str += ch2;

                string str2;
                str2 += ch2;
                str2 += ch1;

                ans += 4 * min(m[str], m[str2]);
            }
        int dunno = 0;
        for (int i = 0; i < CH; i += 1) {
            char ch = i + 'a';
            string s;
            s += ch;
            s += ch;
            if (m[s] & 1) {
                dunno = 1;
                ans += 2 * (m[s] - 1);
            } else
                ans += 2 * m[s];
        }
        cout << dunno << "\n";
        ans += dunno * 2;

        return ans;
    }
};
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