change directory names

21/.formatter.exs

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

21/lib/days/day1.ex

@@ -0,0 +1,17 @@
+defmodule AOC.Day1 do
+  def part1 do
+    AOC.Util.input_integers(1, 1)
+    |> Enum.chunk_every(2, 1, :discard)
+    |> Enum.map(fn [x, y] -> y > x end)
+    |> Enum.count(& &1)
+  end
+
+  def part2 do
+    AOC.Util.input_integers(1, 1)
+    |> Enum.chunk_every(3, 1, :discard)
+    |> Enum.map(&Enum.sum/1)
+    |> Enum.chunk_every(2, 1, :discard)
+    |> Enum.map(fn [x, y] -> y > x end)
+    |> Enum.count(& &1)
+  end
+end

21/lib/days/day2.ex

@@ -0,0 +1,27 @@
+defmodule AOC.Day2 do
+  def parse_input do
+    AOC.Util.input_lines(2, 1)
+    |> Enum.map(fn l ->
+      [dir, amount] = String.split(l, " ")
+      {String.to_atom(dir), String.to_integer(amount)}
+    end)
+  end
+
+  def part1 do
+    parse_input()
+    |> Enum.reduce({0, 0}, fn
+      {:forward, amount}, {distance, depth} -> {distance + amount, depth}
+      {:down, amount}, {distance, depth} -> {distance, depth + amount}
+      {:up, amount}, {distance, depth} -> {distance, depth - amount}
+    end)
+  end
+
+  def part2 do
+    parse_input()
+    |> Enum.reduce({0, 0, 0}, fn
+      {:down, amount}, {distance, depth, aim} -> {distance, depth, aim + amount}
+      {:up, amount}, {distance, depth, aim} -> {distance, depth, aim - amount}
+      {:forward, amount}, {distance, depth, aim} -> {distance + amount, depth + aim * amount, aim}
+    end)
+  end
+end

21/lib/util.ex

@@ -0,0 +1,21 @@
+defmodule AOC.Util do
+  def input_file_name(day, input) do
+    Path.join([File.cwd!(), "inputs", "day#{day}", "input#{input}.txt"])
+  end
+
+  def input_file(day, input) do
+    input_file_name(day, input)
+    |> File.read!()
+  end
+
+  def input_lines(day, input) do
+    input_file_name(day, input)
+    |> File.stream!()
+    |> Enum.map(&String.trim/1)
+  end
+
+  def input_integers(day, input) do
+    input_lines(day, input)
+    |> Enum.map(&String.to_integer/1)
+  end
+end

21/mix.exs

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+defmodule Aoc2021.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :aoc2021,
+      version: "0.1.0",
+      elixir: "~> 1.12",
+      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