public class Solution
extends Object
1079 - Letter Tile Possibilities\.
Medium
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.