<p>You have <code>n</code>&nbsp;&nbsp;<code>tiles</code>, where each tile has one letter <code>tiles[i]</code> printed on it.</p>

<p>Return <em>the number of possible non-empty sequences of letters</em> you can make using the letters printed on those <code>tiles</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> tiles = &quot;AAB&quot;
<strong>Output:</strong> 8
<strong>Explanation: </strong>The possible sequences are &quot;A&quot;, &quot;B&quot;, &quot;AA&quot;, &quot;AB&quot;, &quot;BA&quot;, &quot;AAB&quot;, &quot;ABA&quot;, &quot;BAA&quot;.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> tiles = &quot;AAABBC&quot;
<strong>Output:</strong> 188
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> tiles = &quot;V&quot;
<strong>Output:</strong> 1
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= tiles.length &lt;= 7</code></li>
	<li><code>tiles</code> consists of uppercase English letters.</li>
</ul>

class Solution {
public:
    void solve(string &s,string &temp,unordered_map<string,int> &mp,int k)
    {
        if(temp.size()<=k && !temp.empty())
        {
            mp[temp]++;
            if(temp.size()==k)
                return;
        }

        for(int i=0;i<s.size();i++)
        {
            temp.push_back(s[i]);
            string t;
            t+=s.substr(0,i);
            t+=s.substr(i+1,s.size());
            solve(t,temp,mp,k);
            temp.pop_back();
        }
    }
    int numTilePossibilities(string s) {
        string temp;
        int k=s.size();
        unordered_map<string,int>mp;
        solve(s,temp,mp,k);
        return mp.size();
    }
};
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