A Deterministic Finite Automaton (short DFA) is a finite state machine, that checks if a string of characters follows certain rules. It's bascally another way to represent a Regular Expression, but just have a look at the Swift Playground Book if you want to learn more.

• Just download the Swift Playground App.
• Then download the Playground Book here on your iPad.

I built this Playground Book in a few days as part of my WWDC19 Scholarship Application and luckily got accepted!