<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 = [&quot;un&quot;,&quot;iq&quot;,&quot;ue&quot;]
<strong>Output:</strong> 4
<strong>Explanation:</strong> All the valid concatenations are:
- &quot;&quot;
- &quot;un&quot;
- &quot;iq&quot;
- &quot;ue&quot;
- &quot;uniq&quot; (&quot;un&quot; + &quot;iq&quot;)
- &quot;ique&quot; (&quot;iq&quot; + &quot;ue&quot;)
Maximum length is 4.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> arr = [&quot;cha&quot;,&quot;r&quot;,&quot;act&quot;,&quot;ers&quot;]
<strong>Output:</strong> 6
<strong>Explanation:</strong> Possible longest valid concatenations are &quot;chaers&quot; (&quot;cha&quot; + &quot;ers&quot;) and &quot;acters&quot; (&quot;act&quot; + &quot;ers&quot;).
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> arr = [&quot;abcdefghijklmnopqrstuvwxyz&quot;]
<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>

class Solution {
private:
    int rec(vector<string> arr,int index,vector<int> checker,int len){
        if(index == arr.size()){
            return len;
        }
        cout<<index<<endl;
        vector<int> temp = checker;
        for(char i:arr[index]){
            if(temp[i-'a'] != 0){
                return rec(arr,index+1,checker,len);
            }
            else{
                temp[i-'a'] += 1;
            }
        }

        int ss = (arr[index]).size();
        int np = rec(arr,index+1,checker,len);
        int p = rec(arr,index+1,temp,len+ss);
        return max(np,p);
    }
public:
    int maxLength(vector<string>& arr) {
        vector<string> arr2;
        for(int i = 0;i<arr.size();i++){
            string s = arr[i];
            vector<int> v(26,0);
            bool put = true;
            for(int j = 0;j<s.size();j++){
                if(v[s[j]-'a'] != 0){
                    put = false;
                }
                else{
                    v[s[j]-'a'] += 1;
                }
            }
            if(put == true){
                cout<<s<<endl;
                arr2.push_back(s);
            }
        }
        vector<int> checker(26,0);
        return rec(arr2,0,checker,0);




    }
};
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