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1239-maximum-length-of-a-concatenated-string-with-unique-characters/README.md

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+<h2><a href="https://leetcode.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters/">1239. Maximum Length of a Concatenated String with Unique Characters</a></h2><h3>Medium</h3><hr><div><p>You are given an array of strings <code>arr</code>. A string <code>s</code> is formed by the <strong>concatenation</strong> of a <strong>subsequence</strong> of <code>arr</code> that has <strong>unique characters</strong>.</p>
+
+<p>Return <em>the <strong>maximum</strong> possible length</em> of <code>s</code>.</p>
+
+<p>A <strong>subsequence</strong> is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre><strong>Input:</strong> arr = ["un","iq","ue"]
+<strong>Output:</strong> 4
+<strong>Explanation:</strong> All the valid concatenations are:
+- ""
+- "un"
+- "iq"
+- "ue"
+- "uniq" ("un" + "iq")
+- "ique" ("iq" + "ue")
+Maximum length is 4.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre><strong>Input:</strong> arr = ["cha","r","act","ers"]
+<strong>Output:</strong> 6
+<strong>Explanation:</strong> Possible longest valid concatenations are "chaers" ("cha" + "ers") and "acters" ("act" + "ers").
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre><strong>Input:</strong> arr = ["abcdefghijklmnopqrstuvwxyz"]
+<strong>Output:</strong> 26
+<strong>Explanation:</strong> The only string in arr has all 26 characters.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= arr.length &lt;= 16</code></li>
+	<li><code>1 &lt;= arr[i].length &lt;= 26</code></li>
+	<li><code>arr[i]</code> contains only lowercase English letters.</li>
+</ul>
+</div>