Add solutions for 2022:3 Rucksack Reorganization

Cleaned up version. First one was a bit more spontanious.

2022-elixir/lib/solutions/day_03.ex

@@ -0,0 +1,82 @@
+defmodule Aoc.Solution.Day03 do
+  import Aoc.Utils
+
+  @name "Day 3: Rucksack Reorganization"
+  @behaviour Solution
+
+  @impl Solution
+  def get_name, do: @name
+
+  @impl Solution
+  def present(solution), do: "Sum of priorities is #{solution}"
+
+  @impl Solution
+  def present_again(solution), do: "Sum of the unauthenticated priorities are #{solution}"
+
+  @impl Solution
+  def parse!(raw) do
+    raw
+    |> split_lines()
+  end
+
+  @impl Solution
+  def solve(rucksacks) do
+    rucksacks
+    |> Enum.map(&compartment_pair/1)
+    |> Enum.map(&calculate_compartment_priorities/1)
+    |> Enum.sum()
+  end
+
+  @impl Solution
+  def solve_again(rucksacks) do
+    rucksacks
+    |> Enum.chunk_every(3)
+    |> Enum.map(&calculate_compartment_priorities/1)
+    |> Enum.sum()
+  end
+
+  def compartment_pair(line) do
+    half = line |> String.length() |> div(2)
+    String.split_at(line, half)
+  end
+
+  def calculate_compartment_priorities(compartments) when is_tuple(compartments) do
+    [a, b] =
+      compartments
+      |> Tuple.to_list()
+      |> Enum.map(&distinct/1)
+
+    common_priority(a, b)
+  end
+
+  def calculate_compartment_priorities(compartments) do
+    [a, b, c] =
+      compartments
+      |> Enum.map(&distinct/1)
+
+    common_priority(a, b, c)
+  end
+
+  def distinct(line) do
+    line |> String.codepoints() |> MapSet.new()
+  end
+
+  def priority(char) when is_binary(char), do: char |> String.to_charlist() |> hd |> priority
+  def priority(n) when n > 96, do: n - 96
+  def priority(n), do: n - 38
+
+  def common_priority(a, b, c) do
+    MapSet.intersection(a, b)
+    |> MapSet.intersection(c)
+    |> MapSet.to_list()
+    |> List.first()
+    |> priority
+  end
+
+  def common_priority(a, b) do
+    MapSet.intersection(a, b)
+    |> MapSet.to_list()
+    |> List.first()
+    |> priority
+  end
+end

2022-elixir/test/solutions/day_03_test.exs

@@ -0,0 +1,30 @@
+defmodule Day03Test do
+  use ExUnit.Case
+  doctest Aoc.Solution.Day03
+  import Aoc.Solution.Day03
+
+  @input ~s(
+    vJrwpWtwJgWrhcsFMMfFFhFp
+    jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+    PmmdzqPrVvPwwTWBwg
+    wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+    ttgJtRGJQctTZtZT
+    CrZsJsPPZsGzwwsLwLmpwMDw
+  )
+
+  test "03: Rucksack Reorganization, part 1" do
+    expected = 157
+
+    result = @input |> parse!() |> solve()
+
+    assert result == expected
+  end
+
+  test "03: Rucksack Reorganization, part 2" do
+    expected = 70
+
+    result = @input |> parse!() |> solve_again()
+
+    assert result == expected
+  end
+end