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# 1239. Maximum Length of a Concatenated String with Unique Characters

<https://leetcode.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters>

## Description

You are given an array of strings `arr`. A string `s` is formed by the concatenation of a subsequence of `arr` that has **unique characters**.

Return *the maximum possible length* of `s`.

A **subsequence** is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.

**Example 1:**

```
**Input:** arr = ["un","iq","ue"]
**Output:** 4
**Explanation:** All the valid concatenations are "","un","iq","ue","uniq" and "ique".
Maximum length is 4.
```

**Example 2:**

```
**Input:** arr = ["cha","r","act","ers"]
**Output:** 6
**Explanation:** Possible solutions are "chaers" and "acters".
```

**Example 3:**

```
**Input:** arr = ["abcdefghijklmnopqrstuvwxyz"]
**Output:** 26
```

**Constraints:**

* `1 <= arr.length <= 16`
* `1 <= arr[i].length <= 26`
* `arr[i]` contains only lower case English letters.

## ac

```java
```


---

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