<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 &s1,string &s2)
//     {
//         vector<int> count(26, 0);
//         for (char c : s1) {
//             count[c - 'a']++;
//             if (count[c - 'a'] > 1) {
//                 return false;
//             }
//         }
//         for (char c : s2) {
//             count[c - 'a']++;
//             if (count[c - 'a'] > 1) {
//                 return false;
//             }
//         }
//         return true;
//     }
//     int solve(vector<string>&arr,int i,vector<int>&dp,string temp)
//     {
//         if (i>=arr.size())
//         {
//             return temp.length();
//         }


//         if (hasDuplicate(arr[i],temp))
//         {
//             return solve(arr,i+1,dp,temp);
//         }
        
//         int take=solve(arr,i+1,dp,temp);
//         int skip=solve(arr,i+1,dp,temp+arr[i]);
//         return max(take,skip);
        
        
//     }
//     int maxLength(vector<string>& arr) {
        
//         vector<int>dp(arr.size(),-1);
//         string s="";
//         return solve(arr,0,dp,s);
//     }
// };



class Solution {
public:
    pair<bool,unordered_map<char,int> > unique(string s,unordered_map<char,int>mpp)
    {
        for (int i=0;i<s.length();i++)
        {
            if (mpp.find(s[i])!=mpp.end())
            {
                return {false,mpp};
            }
            else
            {
                mpp[s[i]]++;
            }
        }

        return {true,mpp}; 
    }
    int solve(vector<string>&arr,int index,unordered_map<char,int>&mpp)
    {
        if (index>=arr.size())
        {
            return 0;
        }

        int take=INT_MIN;
        int skip=solve(arr,index+1,mpp);
        auto result=unique(arr[index],mpp);
        if (result.first)
        {
            take=arr[index].length()+solve(arr,index+1,result.second);
        }

        return max(skip,take);
    }
    int maxLength(vector<string>& arr) {

        unordered_map<char,int>mpp;
        return solve(arr,0,mpp);
        
    }
};
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