<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:
    // vector<int> dp; 
    unordered_map< string , int> dp;
    int solve(int idx , string temp , vector<string> &arr, unordered_map<char,int> mp  ){
        if(idx < 0) return 0;

        if(idx == 0 ){
            for(int i = 0 ; i < arr[0].length() ; i++){
                if(mp.find(arr[0][i]) != mp.end()){
                    return   0;
                }
                mp[arr[idx][i]]++;
            }

            return  arr[0].length();
        }

        // if(dp[idx] != -1){
        //     return dp[idx];
        // }
        if(dp.find(temp) != dp.end()){
            return dp[temp];
        }
        unordered_map<char,int> mpFake = mp;

        for(int i = 0 ; i < arr[idx].length() ; i++){
            if(mp.find(arr[idx][i]) != mp.end()){
                cout<<arr[idx][i]<<endl;
                return dp[temp] = solve(idx-1 , temp , arr , mpFake);
            }
            mp[arr[idx][i]] = 1;
        }
        int take =  arr[idx].length() + solve(idx - 1 , temp + arr[idx] ,  arr ,mp);
        int notTake =   solve(idx - 1 , temp ,  arr ,mpFake);
        return dp[temp] = max( take , notTake );


    }
    int maxLength(vector<string>& arr) {
        unordered_map<char,int> mp;
        // dp.resize(arr.size() , -1);
        dp.clear();
        return solve(arr.size() - 1 , "", arr , mp);    
    }
};
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