<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:
    int fac(int n){
          vector<int>dp(n+1);
          dp[0]=0;
          dp[1]=1;
          for(int i=2; i<=n; i++){
              dp[i]=i*dp[i-1];
          }
          return dp[n];
    }
    int numTilePossibilities(string tiles) {
              set<string>st;
              int n=tiles.size();
              for(int i=0; i<(pow(2,n)); i++){
                  string temp="";
                    for(int j=0; j<n; j++){
                           if((i>>j)&1==1){
                                 temp+=tiles[j];
                           }
                    }
                    sort(temp.begin(),temp.end());
                    st.insert(temp);
              }
              int ans=0;
              for(auto it: st){
                   map<char,int>mp;
                   if(it.size()==0){
                    continue;
                   }
                   for(auto jt: it){
                       mp[jt]++;
                   }
                   int a1=fac(it.size());
                   for(auto it: mp){
                       a1=a1/fac(it.second);
                   }
                   ans+=a1;
              }
              return ans;
    }
};
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