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 <= 7tilesconsists of uppercase English letters.
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