<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 {
public:
    int helper(int idx, vector<string>& arr, vector<string>& currResult) {
        unordered_map<char, int> list;
        if(idx<arr.size()){
            cout<<idx<<" "<<currResult.size()<<endl;
            currResult.push_back(arr[idx]);
        }
        else {
            return 0;
        }
        for (int i = 0; i < currResult.size(); i++) {
            for (int j = 0; j < currResult[i].size(); j++) {
                    list[currResult[i].at(j)]++;
                    cout<<currResult[i].at(j) << " "<<list[currResult[i].at(j)]<<endl ;

            }
        }
        cout<<endl;
        bool unique = true;
        for(auto x : list){
            //cout<<x.first << " "<<x.second<<endl ;
            if(x.second > 1){
                unique = false;
                cout<<"false";
                break;
                //list.erase(x.first);
            }
        }
        int nm = 0, nm2 = 0;
        if(unique){
            nm2 = arr[idx].size()+helper(idx+1, arr, currResult); 
            
        }
        currResult.pop_back();
        nm = helper(idx+1, arr, currResult);
               
        return std::max(nm,nm2);
    }

    int maxLength(vector<string>& arr) {
        vector<string> x;

        return helper(0, arr, x);
    }
};
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