1079. Letter Tile Possibilities

https://leetcode.com/problems/letter-tile-possibilities

Description

You have n tiles, where each tile has one letter tiles[i] printed on it.

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

Example 1:

**Input:** tiles = "AAB"
**Output:** 8
**Explanation:** The possible sequences are "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA".

Example 2:

**Input:** tiles = "AAABBC"
**Output:** 188

Example 3:

**Input:** tiles = "V"
**Output:** 1

Constraints:

• 1 <= tiles.length <= 7

• tiles consists of uppercase English letters.

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