Initial release

.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.gitignore

@@ -0,0 +1,36 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+aoc2024-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/
+
+# MacOS
+.DS_Store
+
+# VSCode
+*.code-workspace
+
+# AoC Session File
+.session
+

README.md

@@ -0,0 +1,44 @@
+# Advent of Code 2024 in Elixir
+
+If you've never heard of Advent of Code, you're missing out. Check it out now at [adventofcode.com](https://adventofcode.com/about)!
+
+I mostly do AoC puzzles for fun, generally coding in Python or Rust, but I've also found that it's a great way to get some experience with other programming languages, such as Elixir, Haskell, or Julia.
+
+This repository contains all my solutions to the [AoC 2024](https://adventofcode.com/2024) puzzles using Elixir.
+
+As I'm still learning Elixir, the code may not always be as simple or idiomatic as it could be. If you have suggestions for things I could improve, please don't hesitate to file an issue or submit a PR. Thanks!
+
+## Usage
+
+Make sure you have Elixir and Git installed, then open a terminal and run:
+
+```shell
+git clone https://github.com/ageron/aoc2024-elixir
+cd aoc2024-elixir
+mix aoc2024.run
+```
+
+You can specify days to run if you want, for example this will run days 2, 4, and 6:
+
+```
+mix aoc2024.run 2 4 6
+```
+
+## Getting the data
+
+I've also included a little `get_data.py` utility to automatically download the data of the day, at the right time (you'll get a countdown if you're early). I was too lazy to code it in Elixir, but perhaps I'll port it one day. To use it, just type the following command in a terminal, replacing `{day}` with the day you want:
+
+```
+cd /path/to/this/repository
+python get_data.py 2024 {day}
+```
+
+The script requires the `requests` and `pytz` libraries, which you can install like this:
+
+```
+python -m pip install --user requests pytz
+```
+
+The first time you run `get_data.py`, you will be asked to login to AoC in your browser, [find your session cookie](https://github.com/wimglenn/advent-of-code-wim/issues/1), and save it into a `.session` file in the current directory.
+
+Have fun!

get_data.py

@@ -0,0 +1,72 @@
+#!/usr/bin/env python
+import sys
+import requests
+from datetime import datetime
+from pytz import timezone
+from time import sleep
+from pathlib import Path
+
+# Eric Wastl, the author of Advent-of-Code, asked that if you're automatically
+# querying adventofcode.com (as this script does), then you should include
+# contact details in the User-Agent field. So please replace my name with yours:
+NAME = "Aurélien Geron"
+
+def usage():
+    print("Usage:")
+    print(f"{sys.argv[0]} {{year}} {{day}}")
+    sys.exit(1)
+
+def session_error():
+    print("""Please open your browser, login to adventofcode.com, lookup 
+the session cookie, and save its value to the .session file.
+Here's how to find this cookie in Chrome: right-click > Inspect, select the
+Application tab in the inspector, then in the left menu select
+Storage > Cookies > https://adventofcode.com, and click on session in the list.
+Copy the cookie value: it's a long hexadecimal .""")
+    sys.exit(2)
+
+if len(sys.argv) != 3:
+    usage()
+
+try:
+    year, day = map(int, sys.argv[1:3])
+except ValueError:
+    usage()
+
+session_path = Path(".session")
+if not session_path.is_file():
+    session_error()
+
+eastern = timezone('US/Eastern')
+requested_day = eastern.localize(datetime(year, 12, day))
+
+while True:
+    now = datetime.now(eastern)
+    seconds_left = (requested_day - now).total_seconds()
+    if seconds_left > 0:
+        wait_time = seconds_left % 1
+        if wait_time < 0.5:
+            wait_time += 1
+        sleep(wait_time)
+        print(f"⏰ {int(seconds_left)} ", end="\r");
+    else:
+        break
+
+sleep(1) # just to be safe
+
+url = f"https://adventofcode.com/{year}/day/{day}/input"
+cookies = {"session": open(".session").read().strip()}
+headers = {"User-Agent": NAME}
+request = requests.get(url, cookies=cookies, headers=headers)
+if request.status_code != 200:
+    print(f"HTTP Error {request.status_code}")
+    print(request.text)
+    session_error()
+
+text = request.text
+
+if year == 2023:
+    with open(f"data/day{day:02}.txt", "w") as f:
+        f.write(text)
+else:
+    print(text)

lib/aoc2024/day_01.ex

@@ -0,0 +1,41 @@
+defmodule Aoc2024.Day01 do
+  def parse(input) do
+    numbers =
+      input
+      |> String.split("\n", trim: true)
+      |> Enum.map(fn line ->
+        line
+        |> String.split(~r/\s+/)
+        |> Enum.map(fn int_str ->
+          case int_str |> Integer.parse() do
+            {int, ""} -> int
+            _ -> raise "Invalid integer #{int_str}"
+          end
+        end)
+      end)
+
+    numbers
+    |> Enum.map(&List.to_tuple/1)
+    |> Enum.unzip()
+  end
+
+  def part1({col0, col1}) do
+    sorted_col0 = col0 |> Enum.sort()
+    sorted_col1 = col1 |> Enum.sort()
+
+    Enum.zip(sorted_col0, sorted_col1)
+    |> Enum.map(fn {val0, val1} ->
+      abs(val0 - val1)
+    end)
+    |> Enum.sum()
+  end
+
+  def part2({col0, col1}) do
+    col0
+    |> Enum.map(fn val0 ->
+      count = Enum.count(col1, fn val1 -> val0 == val1 end)
+      count * val0
+    end)
+    |> Enum.sum()
+  end
+end

lib/mix/tasks/aoc2024.run.ex

@@ -0,0 +1,89 @@
+defmodule Mix.Tasks.Aoc2024.Run do
+  use Mix.Task
+
+  @shortdoc "Run all the solutions, or just the ones for the given days"
+  def run(args) do
+    days =
+      if args |> Enum.empty?() do
+        1..25 |> Enum.map(&Integer.to_string/1)
+      else
+        args
+      end
+
+    days |> Enum.each(&run_day/1)
+  end
+
+  defp check_and_pad_day(day_str) do
+    case day_str |> Integer.parse() do
+      {day, ""} when day >= 1 and day <= 25 ->
+        IO.puts("---- Day #{day}")
+        {:ok, day |> Integer.to_string() |> String.pad_leading(2, "0")}
+
+      _ ->
+        {:error, "Invalid day `#{day_str}`"}
+    end
+  end
+
+  defp load_module(padded_day_str) do
+    module = Module.concat([Aoc2024, "Day#{padded_day_str}"])
+
+    if match?({:module, _}, Code.ensure_loaded(module)) do
+      {:ok, module}
+    else
+      {:error, "Module `#{inspect(module)}` is not defined."}
+    end
+  end
+
+  defp load_input(padded_day_str) do
+    file_path = "data/day_#{padded_day_str}.txt"
+
+    case File.read(file_path) do
+      {:ok, content} ->
+        {:ok, content}
+
+      {:error, reason} ->
+        {:error, "Failed to read #{file_path}: #{reason}"}
+    end
+  end
+
+  defp parse_input(module, input) do
+    if function_exported?(module, :parse, 1) do
+      {:ok, module.parse(input)}
+    else
+      {:ok, input}
+    end
+  end
+
+  defp run_part1(module, parsed) do
+    if function_exported?(module, :part1, 1) do
+      result1 = module.part1(parsed)
+      IO.inspect(result1)
+      {:ok, true}
+    else
+      {:error, "Function `#{inspect(module)}.part1/1` is not defined."}
+    end
+  end
+
+  defp run_part2(module, parsed) do
+    if function_exported?(module, :part2, 1) do
+      result2 = module.part2(parsed)
+      IO.inspect(result2)
+      {:ok, true}
+    else
+      {:error, "Function `#{inspect(module)}.part2/1` is not defined."}
+    end
+  end
+
+  defp run_day(day_str) do
+    with {:ok, padded_day_str} <- check_and_pad_day(day_str),
+         {:ok, module} <- load_module(padded_day_str),
+         {:ok, input} <- load_input(padded_day_str),
+         {:ok, parsed_input} <- parse_input(module, input),
+         {:ok, _success} <- run_part1(module, parsed_input),
+         {:ok, _success} <- run_part2(module, parsed_input) do
+    else
+      {:error, msg} ->
+        IO.puts("Error: #{msg}")
+    end
+  end
+end

mix.exs

@@ -0,0 +1,28 @@
+defmodule Aoc2024.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :aoc2024,
+      version: "0.1.0",
+      elixir: "~> 1.17",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

test/aoc2024_test.exs

@@ -0,0 +1,8 @@
+defmodule Aoc2024Test do
+  use ExUnit.Case
+  doctest Aoc2024
+
+  test "greets the world" do
+    assert Aoc2024.hello() == :world
+  end
+end

test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()