Advent of Code F# – Day 23

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Yan Cui

I help clients go faster for less using serverless technologies.

ps. look out for all my other solutions for Advent of Code challenges here.

 

Day 23

See details of the challenge here.

Today’s input looks like this:

cpy a b
dec b
cpy a d
cpy 0 a
cpy b c
inc a

..

Today’s challenge is an extension to Day 12, where we have introduced a new instruction for toggle (tgl). To make toggling logic simpler let’s introduce a union type to represent the different instructions we can receive and write a function parse them.

Next, let’s add a toggle function to toggle a given instruction and modify the execute function from Day 12 to work with the union type and support the new tgl instruction as well.

Now we can solve part 1.

let part1 = (execute [ "a”, 7 ] inputs).[�["a”]strong>

 

Part 2

The safe doesn’t open, but it does make several angry noises to express its frustration.

You’re quite sure your logic is working correctly, so the only other thing is… you check the painting again. As it turns out, colored eggs are still eggs. Now you count 12.

As you run the program with this new input, the prototype computer begins to overheat. You wonder what’s taking so long, and whether the lack of any instruction more powerful than “add one” has anything to do with it. Don’t bunnies usually multiply?

Anyway, what value should actually be sent to the safe?

As the description eludes to, if we use 12 as initial input it might take a while to run.. and the naive approach of just executing the logic as before, ie

let part2 = (execute [ �[ "a”, 12 ]uts).[“a�["a”]ng>

took a good 4 minutes to run on my 2015 MBP.

If you add a few printfn statements and you’ll a few blocks of instructions that repeat for many cycles, eg.

cpy b c
inc a
dec c
jnz c -2
dec d
jnz d -5

you can add a short-circuit when you see this happen and replace it with the equivalent of a = b * d (as the description eluded to).

 

Links

 

Whenever you’re ready, here are 4 ways I can help you:

  1. If you want a one-stop shop to help you quickly level up your serverless skills, you should check out my Production-Ready Serverless workshop. Over 20 AWS Heroes & Community Builders have passed through this workshop, plus 1000+ students from the likes of AWS, LEGO, Booking, HBO and Siemens.
  2. If you want to learn how to test serverless applications without all the pain and hassle, you should check out my latest course, Testing Serverless Architectures.
  3. If you’re a manager or founder and want to help your team move faster and build better software, then check out my consulting services.
  4. If you just want to hang out, talk serverless, or ask for help, then you should join my FREE Community.

 

1 thought on “Advent of Code F# – Day 23”

  1. Pingback: Advent of Code F# – Day 25 | theburningmonk.com

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