<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 factorial[8] = {1, 1, 2, 6, 24, 120, 720, 5040};
    int getans(int hash[]) {
        int sum = 0;
        for (int i = 0; i < 26; i++) {
            sum += hash[i];
        }
        sum = factorial[sum];
        for (int i = 0; i < 26; i++) {
            sum /= factorial[hash[i]];
        }
        return sum;
    }
    int numTilePossibilities(string tiles) {
        int n = tiles.length();
        int ans = 0;
        // sort(tiles.begin(), tiles.end());
        unordered_set<string> st;
        for (int i = 1; i < (1 << n); i++) {
            int hash[26] = {0};
            string temp = "";
            for (int j = 0; j < n; j++) {
                if ((i >> j) & 1) {
                    temp += tiles[j];
                    hash[tiles[j] - 'A']++;
                }
            }
            sort(temp.begin(), temp.end());
            if (st.find(temp) == st.end()) {
                ans += getans(hash);
                st.insert(temp);
            }
        } 
        
        return ans;
    }
};
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