Day/2022/13

2022/day13/.formatter.exs

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

2022/day13/.gitignore

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+# 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").
+day13-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/
+
+day13

2022/day13/README.md

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+# Day 13
+
+[Challenge link](https://adventofcode.com/2022/day/13).
+
+How to run:
+
+Put your data into 'data.txt' (in the same directory as this readme file).
+
+```sh
+mix escript.build && ./day13
+```

2022/day13/lib/comparator/comparator.ex

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+defmodule Comparator do
+  @spec compare(any(), any()) :: boolean
+  def compare(l, r) do
+    case check_order(l, r) do
+      :ok -> true
+      :inconclusive -> true
+      :wrong -> false
+    end
+  end
+
+  @spec check_order(any(), any()) :: :ok | :wrong | :inconclusive
+  defp check_order(l, r) do
+    case {l, r} do
+      {a, b} when is_integer(a) and is_integer(b) -> compare_ints(a, b)
+      {a, b} when is_list(a) and is_list(b) -> compare_lists(a, b)
+      {a, b} when is_integer(a) and is_list(b) -> check_order([a], b)
+      {a, b} when is_list(a) and is_integer(b) -> check_order(a, [b])
+    end
+  end
+
+  @spec compare_ints(integer(), integer()) :: :ok | :wrong | :inconclusive
+  defp compare_ints(a, b) do
+    cond do
+      a < b -> :ok
+      a > b -> :wrong
+      a == b -> :inconclusive
+    end
+  end
+
+  @spec compare_lists([], []) :: :ok | :wrong | :inconclusive
+  defp compare_lists(a, b) do
+    cond do
+      a == [] and b == [] -> :inconclusive
+      a == [] -> :ok
+      b == [] -> :wrong
+      true -> compare_lists_by_element(a, b)
+    end
+  end
+
+  @spec compare_lists_by_element([], []) :: :ok | :wrong | :inconclusive
+  defp compare_lists_by_element(a, b) do
+    first_a = Enum.at(a, 0)
+    first_b = Enum.at(b, 0)
+    order = check_order(first_a, first_b)
+
+    if order != :inconclusive do
+      order
+    else
+      compare_lists(Enum.drop(a, 1), Enum.drop(b, 1))
+    end
+  end
+end

2022/day13/lib/main.ex

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+defmodule Day13.CLI do
+  def main(_args) do
+    File.stream!("data.txt") |> Parser.data() |> solve()
+    :ok
+  end
+
+  defp solve(contents) do
+    IO.write("task #1 solution: ")
+    Task1.solution(contents) |> IO.puts()
+
+    IO.write("task #2 solution: ")
+    Task2.solution(contents) |> IO.puts()
+  end
+end

2022/day13/lib/parser.ex

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+defmodule Parser do
+  @spec lines(File.Stream) :: Stream.t()
+  def lines(fstream) do
+    fstream
+    |> Stream.map(&String.trim/1)
+  end
+
+  @spec data(Stream.t()) :: Stream.t()
+  def data(lines) do
+    lines |> Enum.chunk_every(3) |> Enum.map(fn l -> parse_pair(l) end)
+  end
+
+  @spec parse_pair([String.t()]) :: {[], []}
+  defp parse_pair(s) do
+    [first, second] = s |> Enum.take(2)
+    {parse_packet(first), parse_packet(second)}
+  end
+
+  @spec parse_packet(String.t()) :: []
+  defp parse_packet(s) do
+    Code.eval_string(s) |> elem(0)
+  end
+end

2022/day13/lib/task1/task1.ex

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+defmodule Task1 do
+  @spec solution([{[], []}]) :: integer()
+  def solution(pairs) do
+    Enum.map(pairs, fn {l, r} -> Comparator.compare(l, r) end)
+    |> Enum.with_index()
+    |> Enum.filter(fn {x, _} -> x end)
+    |> Enum.map(fn {_, i} -> i + 1 end)
+    |> Enum.sum()
+  end
+end

2022/day13/lib/task2/task2.ex

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+defmodule Task2 do
+  @spec solution([{[], []}]) :: integer()
+  def solution(pairs) do
+    Enum.reduce(pairs, [], fn {l, r}, acc -> [l] ++ [r] ++ acc end)
+    |> with_new_pairs()
+    |> Enum.sort(&Comparator.compare/2)
+    |> Enum.with_index()
+    |> Enum.filter(fn {x, _} -> x == [[2]] or x == [[6]] end)
+    |> Enum.map(fn {_, i} -> i + 1 end)
+    |> Enum.reduce(1, fn x, acc -> x * acc end)
+  end
+
+  @spec with_new_pairs([]) :: []
+  defp with_new_pairs(list) do
+    [[[2]]] ++ [[[6]]] ++ list
+  end
+end

2022/day13/mix.exs

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+defmodule Day13.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :day13,
+      version: "0.1.0",
+      elixir: "~> 1.14",
+      start_permanent: Mix.env() == :prod,
+      deps: deps(),
+      escript: escript()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  defp escript do
+    [main_module: Day13.CLI]
+  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

2022/day13/test/test_helper.exs

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+ExUnit.start()