jacks aoc ramble - 2022 day 3

day 3

3rd night in a row up until 1:30am .-.

why do i make these choices

oh well this one was nice, got to pull out more functional programming goodies today, and found reviewing others submissions a little more engaging than previous days, hopefully that continues!

click to view my solution

given the sample input:

vJrwpWtwJgWrhcsFMMfFFhFp
jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
PmmdzqPrVvPwwTWBwg
wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
ttgJtRGJQctTZtZT
CrZsJsPPZsGzwwsLwLmpwMDw

assuming input is the above as one big string,

rucksacks =
  input
  |> String.split("\n", trim: true)
  |> Enum.map(&String.split(&1, "", trim: true))

a pretty simple input parse today, just split on newlines, and then split each string into a list of characters

[
  ["v", "J", "r", "w", "p", "W", "t", "w", "J", "g", "W", "r", "h", "c", "s", "F", "M", "M", "f",
   "F", "F", "h", "F", "p"],
  ["j", "q", "H", "R", "N", "q", "R", "j", "q", "z", "j", "G", "D", "L", "G", "L", "r", "s", "F",
   "M", "f", "F", "Z", "S", "r", "L", "r", "F", "Z", "s", "S", "L"],
  ["P", "m", "m", "d", "z", "q", "P", "r", "V", "v", "P", "w", "w", "T", "W", "B", "w", "g"],
  ["w", "M", "q", "v", "L", "M", "Z", "H", "h", "H", "M", "v", "w", "L", "H", "j", "b", "v", "c",
   "j", "n", "n", "S", "B", "n", "v", "T", "Q", "F", "n"],
  ["t", "t", "g", "J", "t", "R", "G", "J", "Q", "c", "t", "T", "Z", "t", "Z", "T"],
  ["C", "r", "Z", "s", "J", "s", "P", "P", "Z", "s", "G", "z", "w", "w", "s", "L", "w", "L", "m",
   "p", "w", "M", "D", "w"]
]

another day, another list of lists

defmodule Rucksack do
  def item_to_priority(item) do
    item |> String.to_charlist() |> Enum.at(0) |> item_number_to_priority
  end

  def item_number_to_priority(number) when number >= 97, do: number - 96
  def item_number_to_priority(number), do: number - 38
end

once we find the duplicate item in the rucksack(s), we’ll need to map that to some priority number

here, i go from string -> charlist -> single char, and then use some sneaky guard clauses to do math on the single char value which maps it from its value in ascii, to the priority number

part 1

rucksacks
|> Enum.map(fn rucksack ->
  rucksack
  |> Enum.split(round(length(rucksack) / 2))
  |> Tuple.to_list()
  |> Enum.map(&MapSet.new(&1))
  |> Enum.reduce(&MapSet.intersection(&1, &2))
  |> Enum.at(0)
  |> Rugsack.item_to_priority()
end)
|> Enum.sum() # -> 157

i do a lot here

first, i want to map over each rucksack, since for part one we are concerned about splitting up a rucksack into two chunks, and finding a duplicate between each chunk

i use Enum.split to split the rucksack into two chunks, which gives me a tuple, so i use Tuple.to_list() to turn it back into a list i can iterate over

i then, convert each list into a MapSet, since i want to perform a [set operation] to find the duplicate

i then reduce my list of two items down to one, using a reducer that passes its values to MapSet.intersection, which will end up only reducing once, since the first item will be the accumulator, and the second item will be the only other value the reducer handles

after this operation i am left with a single MapSet, with only a single value within it, the duplicate

i use Enum.at(0) to pluck out the single item from the MapSet, passing it to my utility function to convert from item -> priority number

i do this for every rucksack, and compute the sum of the list of priorities

part 2

rucksacks
|> Enum.chunk_every(3)
|> Enum.map(fn rucksacks ->
  rucksacks
  |> Enum.map(&MapSet.new(&1))
  |> Enum.reduce(&MapSet.intersection(&1, &2))
  |> Enum.at(0)
  |> Rugsack.item_to_priority()
end)
|> Enum.sum() # -> 70

this is similar to the above, however, i use Enum.chunk_every(3) to convert my list of rucksacks into a list of lists of rucksacks, each nested list having a length of 3

i iterate over this list of lists, and convert each rucksack in the list of 3 to a MapSet, like before, but since i’m not splitting it into two, i use Enum.reduce with MapSet.intersection again, but this time i’m reducing 3 MapSets to a single MapSet

then, i do the same as before, pluck out the answer, get the priority, and sum everything, ezdubz

the full solution can be found [here]

others

[Mudkip/AdventOfCode] python

a nice and compact solution

def part1():
    input = open("3.in", "r").read().splitlines()
    rucksacks = ((set(list(x[:len(x)//3])), set(list(x[len(x)//2:]))) for x in input)
    prios = (ord((rucksack[0] & rucksack[1]).pop())-96 for rucksack in rucksacks)
    normalize = (prio if prio > 0 else prio+58 for prio in prios)
    return sum(normalize)

def part2():
    input = open("3.in", "r").read().splitlines()
    groups = [input[i:i+3] for i in range(0,len(input), 3)]
    badges = [(set(group[0]) & set(group[1]) & set(group[2])) for group in groups]
    prios = (ord(badge.pop())-96 for badge in badges)
    normalize = (prio if prio > 0 else prio+58 for prio in prios)
    return sum(normalize)

so nice and compact i can comfortably include it inline within this page without it filling up much space

a bit code golfy, but sometimes thats the vibe

[krbarter/Advent-Of-Code-2022] python

some set operations, and being sneaky using a string to map the resulting duplicate to the value

part 3 is heading into code golf territories, but i usually feel that whenever i see a complicated list comprehension statement that i haven’t authored :)

[nint8835/AdventOfCode2022] f# & python

feelin’ a lot like my solution with regards to the mapping / usage of set intersections

however the same string map trick kent used, is also used here, nice and compact!

i prefer this implementation of the string map because i am a functional programming fiend

[hamzahap/AdventOfCode2022] sheets

opening up this sheet on my laptop makes it unhappy and loud initially

but hamzah is out here still on that sheets grind

however,

[3:38 AM] Hking: Motivation to stop doing Sheets is very high rn

this statement from a very up late hamzah might indicate the end of the sheets reign?

time will tell

[TheCrypticCanadian/advent-of-code-2022] python

input parsing looks to be more than whats needed, but still using set operations, so clean

[STollenaar/AdventOfCode2022] golang

it seems sven have the same realization as myself and mudkip, but

[12:30 PM] Secure Cluster Nerd 5000: yuup I thought the same. but with GO there isn’t really a nice quick buildin way to do that

therefore his solution looks like the solution of someone who has sets in their head, but not actually using sets

its still compact so nice

[zcvaters/adventofcode2022] swift

zach had a pretty gnarly function to go from rucksack item -> priority, but by the time i am writing this, its much cleaner :)

swift has sets!, which are being used here, although using [intersection] would be cleaner imo

[chadmroberts88/advent-of-code-2022] typescript

clean little ts solution, almost functional if that forEach usage could be a reduce instead :)

[mathieuboudreau/advent] python notebook

set and ord, the python tricks that make this solution clean

but whats this, & usage to do intersections on the sets!

now thats mathy

[Keenan-Nicholson/AdventOfCode] typescript

[12:31 PM] keeborg: As a mathematician I’m disappointed my first thought was not set intersection

keenans solution does not use sets, and he’s sad it doesn’t use sets

i still think its nice though <3

[CameronSquires/AdventOfCode2022] python

a bitta [indent hadouken] going on here

[joel1842/advent-of-code-2022] python

joel keeps up the list comprehension grind yet again

[ecumene/advent_of_code] python notebook

mitch out here managing to be the first person on the muncs leaderboard to complete both part 1 nand 2, nice

he has also blessed us with another ai image:

prompt: an elf filling bags with supplies for a journey into the jungle

thank you mitchell, very cool

[canetoads.ca] javascript

interesting, constructing a map from item -> priority programmatically

mixing arrow functions and full fat functions inline, tsk tsk

but its still nice and compact, and set-intersectiony, so nice

[apreynolds1989/AdventOfCode2022] typescript

another day that is so close to being functional! make those forEach statements reducers!

a nice solution though, and catches the strict of char code conversion depending on if upper or lower case

[lilmert/aoc] rust

marty’s aoc utils are :clean:

rfind on the ALPHABET is :clean:

[RyanBrushett/adventofcode2022] ruby

its ruby so im biased for the third day in the row, that this is clean

i keep using the word clean quite a bit

probably the neatest solution that prepares a priority map beforehand
letters = ('a'..'z').to_a.concat(('A'..'Z').to_a)
priorities = letters.each_with_object({}).with_index do |(letter, hash), index|
   hash[letter] = index + 1
end
and uses & for set operations

nice

[ajhynes7/advent-of-code-2022] julia

julia and ruby are def. the nicest here to skim through, probably because syntactically its similar to my own solution :)

a top level intersect function, interesting

i like the top level first function usage too

im gonna say it

clean

[devthedevel/advent_of_code] typescript

Dev: Also no //@ts-ignore this time @Jack Harrhy

the clouds have heeded my advice, i am forever blessed

[DanielPower/AdventOfCode2022] haskell

daniel was late on this one, tsk tsk, too much osu

the function name uncurry makes me laugh

many util functions, but util functions are nice and small

very composed of functions, very functional, who would have guessed from someone doing their solution in haskell

if you want to have your repo added for me to make a note of / talk about here (or have you repo removed), reach out:

email -> me@jackharrhy.com

discord -> <i>jack arthur null</i>#7539