Advent of Code 2024 - Day 01

2024/01.livemd

Phil-Bastian Berndt

@pehbehbeh

adventofcode

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Advent of Code 2024 - Day 01

Mix.install([
  {:req, "~> 0.5"}
])

Input

opts = [headers: [{"cookie", "session=#{System.fetch_env!("LB_AOC_SESSION")}"}]]
puzzle_input = Req.get!("https://adventofcode.com/2024/day/1/input", opts).body

{list_left, list_right} =
  puzzle_input
  |> String.split("\n", trim: true)
  |> Enum.map(fn row ->
    String.split(row)
    |> Enum.map(&amp;String.to_integer/1)
    |> List.to_tuple()
  end)
  |> Enum.unzip()

Part 1

Enum.zip(
  Enum.sort(list_left), 
  Enum.sort(list_right)
)
|> Enum.map(fn {a, b} -> abs(a - b) end)
|> Enum.sum()

Part 2

frequencies = Enum.frequencies(list_right)

Enum.reduce(list_left, 0, fn a, acc ->
  acc + a * Map.get(frequencies, a, 0)
end)

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