Solve first two days of 2019 in Elixir

1 files changed, 32 insertions, 0 deletions

diff --git a/aoc-2019-elixir/lib/day01.ex b/aoc-2019-elixir/lib/day01.ex
new file mode 100644
index 0000000..6545f19
--- /dev/null
+++ b/aoc-2019-elixir/lib/day01.ex
@@ -0,0 +1,32 @@
+defmodule Day01 do
+  @spec part1([integer]) :: integer
+  def part1(input) do
+    input
+    |> Enum.map(&naive_fuel_requirement/1)
+    |> Enum.sum()
+  end
+
+  @spec part2([integer]) :: integer
+  def part2(input) do
+    input
+    |> Enum.map(&recursive_fuel_requirement/1)
+    |> Enum.sum()
+  end
+
+  defp naive_fuel_requirement(mass) do
+    div(mass, 3) - 2
+  end
+
+  defp recursive_fuel_requirement(mass) do
+    fuel_mass = div(mass, 3) - 2
+
+    case fuel_mass do
+      n when n <= 0 -> 0
+      _ -> fuel_mass + recursive_fuel_requirement(fuel_mass)
+    end
+  end
+end
+
+input = Util.Input.read_numbers("day01")
+input |> Day01.part1() |> IO.inspect()
+input |> Day01.part2() |> IO.inspect()