<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 n;
bool isduplicate(string s,string temp){
    map<char,bool>mp,check;
    for(int i=0;i<s.length();i++){
        if(check[s[i]]==true){
            return true;
        }
        check[s[i]]=true;
    }
    for(int i=0;i<temp.length();i++){
        mp[temp[i]]=true;
    }
    for(int i=0;i<s.length();i++){
        if(mp[s[i]]){
            return true;
        }
    }
      for(int i=0;i<s.length();i++){
        mp[s[i]]=true;
    }
return false;
}
    int solve(vector<string>& arr,int ind,string temp,vector<int>&dp){
        if(ind==n){
            return temp.length();
        }
        // if(dp[ind]!=-1){
        //     return dp[ind];
        // }
        int take =0;
        int n_take=0;
        if(!isduplicate(arr[ind],temp)){
          take = solve(arr,ind+1,temp+arr[ind],dp);
        }
       n_take = solve(arr,ind+1,temp,dp);
        return max(take,n_take);

    }
    int maxLength(vector<string>& arr) {
     string temp="";
     n=arr.size();
    vector<int>dp(n+1,-1);
     return solve(arr,0,temp,dp);
    }
};
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