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

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

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`.

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" ("un" + "iq")
- "ique" ("iq" + "ue")
Maximum length is 4.
```

Example 2:

```Input: arr = ["cha","r","act","ers"]
Output: 6
Explanation: Possible longest valid concatenations are "chaers" ("cha" + "ers") and "acters" ("act" + "ers").
```

Example 3:

```Input: arr = ["abcdefghijklmnopqrstuvwxyz"]
Output: 26
Explanation: The only string in arr has all 26 characters.
```

Constraints:

• `1 <= arr.length <= 16`
• `1 <= arr[i].length <= 26`
• `arr[i]` contains only lowercase English letters.