Solves an InterviewCake.com problem that returns all of the permutations of a
string input. The problem states that it's acceptable to assume that your input
string will not have repeated characters, which is why using a Set is
acceptable. I like this solution because it builds a permutations tree and then
assembles all of the permutations by doing a DFT over that tree.
While I've done these algorithms before, I'm preparing for an on-site with
DeepMind, so I created a subdirectory called deepmind where I'm storing my
second attempts at these problems. The idea of storing them in a second
directory is to remove the urge to check my existing solutions that also exist
in this repository.
