<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 ans=0;
    map<pair<int,string>,int>dp;
    int func(int ind,vector<string>& arr,string str,int n)
    {
        if(ind==n)
        {
            return 0;
        }
        if(dp.find({ind,str})!=dp.end())return dp[{ind,str}];
        unordered_map<char,int>mpp;
        dp[{ind,str}]=func(ind+1,arr,str,n);
        for(int i=0;i<str.size();i++)mpp[str[i]]++;
        bool flag=true;
        for(int i=0;i<arr[ind].size();i++)
        {
            if(mpp.find(arr[ind][i])!=mpp.end())
            {
                flag=false;
                
                break;
            }
            mpp[arr[ind][i]]++;
        }
        if(flag)
        {
            int p=arr[ind].size();
            dp[{ind,str}]=max(dp[{ind,str}],p+func(ind+1,arr,str+arr[ind],n));
        }
        return dp[{ind,str}];
    }
    int maxLength(vector<string>& arr) {
        int n=arr.size();
        return func(0,arr,"",n);
    
    }
};
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