# ---
# title: 1239. Maximum Length of a Concatenated String with Unique Characters
# id: problem1239
# author: Tian Jun
# date: 2020-10-31
# difficulty: Medium
# categories: Backtracking, Bit Manipulation
# link: <https://leetcode.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters/description/>
# hidden: true
# ---
# 
# Given an array of strings `arr`. String `s` is a concatenation of a sub-
# sequence of `arr` which have **unique characters**.
# 
# Return _the maximum possible length_ of `s`.
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: arr = ["un","iq","ue"]
#     Output: 4
#     Explanation: All possible 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.
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
