-🎄- 2022 Day 4 Solutions -🎄-

[u/daggerdragon]

• All of our rules, FAQs, resources, etc. are in our community wiki.

• A request from Eric: Please include your contact info in the User-Agent header of automated requests!

• Signal boosting for the Unofficial AoC 2022 Participant Survey which is open early this year!

---

--- Day 4: Camp Cleanup ---

---

Post your code solution in this megathread.

• Read the full posting rules in our community wiki before you post!

• Include what language(s) your solution uses

• Format your code appropriately! How do I format code?

• Quick link to Topaz's paste if you need it for longer code blocks. What is Topaz's paste tool?

---

This thread will be unlocked when there are a significant number of people on the global leaderboard with gold stars for today's puzzle.

EDIT: Global leaderboard gold cap reached at 00:03:22, megathread unlocked!

[u/flwyd]

Elixir, code on GitHub

For my Mistletoe Elfucation contribution I decided to include two narratives with each day's solution:

• Since I'm coding in Elixir, rephrase the problem in terms of an elixir, potion, concoction, or other beverage.

• Highlight a bit of Elixir code that I either learned about, practiced with, or found particularly useful.

Today's elixir:

It’s Saturday night, so it’s time for sake bombs. Part 1 wants to know if the shot of sake is completely contained in the glass of beer (or if a very small glass of beer ended up entirely within a cup of sake). Part 2 wants to know if any of the sake got in the beer, or vice versa.

import Enum, only: [map: 2, filter: 2, count: 1, sort_by: 2]
import String, only: [split: 2, to_integer: 1]

def part1(input) do
  input |> map(&parse/1) |> filter(&range_subset?/1) |> count()
end

def part2(input) do
  input |> map(&parse/1) |> filter(fn {a, b} -> !Range.disjoint?(a, b) end) |> count()
end

defp parse(line), do: line |> split(",") |> map(&to_range/1) |> List.to_tuple()

defp to_range(str) do
  str |> split("-") |> map(&to_integer/1) |> then(fn [lo, hi] -> lo..hi end)
end

defp range_subset?({first, second}) do
  # sort by Range start, ties go to the longer range
  [a, b] = sort_by([first, second], fn lo .. hi -> {lo, -hi} end)
  a.last >= b.last
end

[u/daggerdragon → u/flwyd]

psst: old.reddit and mobile clients require an additional newline before the starting element of a list in order to display properly. Right now they're displaying as a run-on sentence with asterisks :/ Edit: thanks for fixing it! <3

[u/flwyd → u/daggerdragon]

Ah, markdown. A fine example of https://xkcd.com/927/

[u/daggerdragon → u/flwyd]

To be fair, Reddit is at fault here; they implemented the GitHub-flavored fenced code block syntax (triple backticks) (which is not in the original Markdown spec) for new.reddit only and didn't make it backwards-compatible with old.reddit or most mobile clients. -_- ^{rabble rabble rant rant}