LeetCode 5087: Letter Tile Possibilities in Swift

This is a scrabble challenge. What are the different combinations of letters that can be derived from a set of letters.

For example with input tiles of “AAB” there are the following possibilities:

“A”

“B”

“AA”

“AB”

“BA”

“AAB”

“ABA”

“BAA”

Note that there are no repetitions for the tile possibilities here!

Dictionaries

Dictionaries in Swift typically have a lookup of O(1). This makes it a good candidate for this problem.

The setup

We can place each of our tiles into a frequency array, and can use the great initializer in Swift that allows us to give a default for each tile (making the syntax easy to read):

The algorithm

This algorithm for the input “AAB” is as follows: