<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:
    bool hasDuplicate(string &str,string &temp)
    {
        unordered_map<int,int> mp1;
        for(auto st:str)
        {
            if(mp1[st-'a']>=1)
            return true;
            mp1[st-'a']++;
        }
        for(auto ch:temp)
        {
            if(mp1[ch-'a'] > 0)
            return true;
        }
        return false;
    }
    int solve(int i,vector<string> arr, int n,string temp)
    {
        if(i>=n)
        return temp.size();

        int incl = 0;
        int excl = 0;
        
        if(hasDuplicate(arr[i],temp))
        {
            // agr duplicate h to sirf hme exclude hee krna h
            excl =  solve(i+1,arr,n,temp);
        }
        else{
            //1 to exclude h
            excl = solve(i+1,arr,n,temp);

            //agr include krna h
            incl = solve(i+1,arr,n,temp+arr[i]);
        }
        return max(incl,excl);
    }
    int maxLength(vector<string>& arr) {
        int n=arr.size();
        string temp = "";
        int i=0;
        return solve(i,arr,n,temp);
    }
};
286921