<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:
    unordered_set<string>st;
    void permutations(string s,int idx)
    {
        int n = s.size();
        if(idx==n)
        {
            st.insert(s);
        }
        for(int i=idx;i<n;i++)
        {
            swap(s[i],s[idx]);
            permutations(s,idx+1);
            swap(s[i],s[idx]);
        }
    }
    void subsequences(string s,string temp,int idx)
    {
        if(idx==s.size())
        {
            if(temp.size()>0)
            {
                st.insert(temp);
                permutations(temp,0);
            }
            return;
        }

        temp.push_back(s[idx]);
        subsequences(s,temp,idx+1);
        temp.pop_back();

        subsequences(s,temp,idx+1);
    }
    int numTilePossibilities(string tiles) {
        int n = tiles.size();
        permutations(tiles,0);
        string temp = "";
        subsequences(tiles,temp,0);
        reverse(tiles.begin(),tiles.end());
        temp = "";
        subsequences(tiles,temp,0);
        for(auto &it:st)
        {
            cout<<it<<" ";
        }
        cout<<endl;
        return st.size();
    }
};
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