Solution: Letter Tile Possibilities

Let’s solve the Letter Tile Possibilities problem using the Subsets pattern.

We'll cover the following

Statement

You are given a string, tiles, consisting of uppercase English letters. You can arrange the tiles into sequences of any length (from 1 to the length of tiles), and each sequence must include at most one tile, tiles[i], from tiles.

Your task is to return the number of possible non-empty unique sequences you can make using the letters represented on tiles[i].

Constraints:

  • 1≤1 \leq tiles.length ≤7\leq 7

  • The tiles string consists of uppercase English letters.

Solution

This problem would have been straightforward if the tiles had no duplicates and we only needed to find sequences of the same length as the given tiles. In that case, we could simply calculate the total unique sequences using n!n! (where nn is the length of the tiles).

Level up your interview prep. Join Educative to access 70+ hands-on prep courses.