letter-tile-possibilities

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Algorithms

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

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

&nbsp;
Example 1:

<pre>
Input: tiles = &quot;AAB&quot;
Output: 8
Explanation: 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>

Example 2:

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

Example 3:

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

&nbsp;
Constraints:

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

numTilePossibilities

Letter Tile Possibilities

Hash Table

String

Backtracking

Counting

你有一套活字字模&nbsp;<code>tiles</code>，其中每个字模上都刻有一个字母&nbsp;<code>tiles[i]</code>。返回你可以印出的非空字母序列的数目。

注意：本题中，每个活字字模只能使用一次。

&nbsp;

示例 1：

<pre>
输入："AAB"
输出：8
解释：可能的序列为 "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA"。
</pre>

示例 2：

<pre>
输入："AAABBC"
输出：188
</pre>

示例 3：

<pre>
输入："V"
输出：1</pre>

&nbsp;

提示：

<ul>
	<li><code>1 &lt;= tiles.length &lt;= 7</code></li>
	<li><code>tiles</code> 由大写英文字母组成</li>
</ul>