bjorng

Erlang Core Team

Advent of Code 2024 - Day 25

This wraps up Advent of Code 2024 for me. Looking back on the puzzles, here are the ones I found to be the hardest:

The most fun puzzles for me were:

It turns out that three of the puzzles are on both lists.

bjorng/advent-of-code/blob/main/2024/day25/lib/day25.ex

defmodule Day25 do
  def part1(input) do
    {keys, locks} = parse(input)
    Enum.flat_map(locks, fn lock ->
      Enum.map(keys, fn key ->
        Enum.zip_with(key, lock, fn a, b -> a + b > 5 end)
        |> Enum.any?(&(&1))
      end)
    end)
    |> Enum.reject(&(&1))
    |> Enum.count
  end

  defp parse(input) do
    input
    |> String.split("\n\n", trim: true)
    |> Enum.map(fn block ->
      lock? = match?("#" <> _, block)
      String.split(block, "\n", trim: true)
      |> Enum.map(fn line ->

This file has been truncated. show original

4 comments

#advent-of-code #2024

11 249 4

2024-12-26 14:15:56 UTC

Most Liked

rvnash

Yay, 50 stars. My first year trying my hand at AOC. 23 successes, and 2 times I relied on you guys to help me out. Thanks all, it was fun.

github.com

rvnash/aoc2024/blob/main/lib/d25.ex

defmodule D25 do
  @aoc_year "2024"
  @aoc_day __MODULE__ |> to_string() |> String.slice(-2..-1)
  # 0 is the file itself
  @content 0

  def read_input do
    content = %{
      0 => File.read!("./lib/#{@aoc_day}.txt"),
      1 => """
      #####
      .####
      .####
      .####
      .#.#.
      .#...
      .....

      #####
      ##.##

This file has been truncated. show original

Any observations on doing this in Elixir vs. other languages? I noticed the most elegant solutions posted here were a tight sequence of transformers taking the input data through Lists, Maps, MapSets, recursive traversals or searches, and composing it all back to the required output. I know other languages have these parts, but often I found myself smiling in satisfaction at the solutions you all posted.

Happy Holidays

Post #2

code-shoily

I did this in F# and if I had to do it in Elixir, it would have been almost identical in code, with some strong typing and point free pipes.

This is the first year where I have done more solution in a non-Elixir programming language and loved it. I will actually write a post about my experiences.

Post #3

liamcmitchell

Wooooooo, bittersweet that there is no part 2 but really happy to have finished

After all the challenges involving bit operations, I realised the keys and locks can be encoded as a single integer and a bitwise AND will check if there are any overlaps.

Post #4

Where Next?

View thread on forum (has 4 responses!)

advent-of-code

2024

Home Learning Resources>Coding Challenges

#advent-of-code #2024

11 252 4

Last post

Advent of Code 2024 - Day 25

bjorng

Advent of Code 2024 - Day 25

Most Liked

rvnash

code-shoily

liamcmitchell

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