2 files changed, 37 insertions, 0 deletions
diff --git a/AoC2022/04/makefile b/AoC2022/04/makefile
index a7661bd..6516fa4 100644
--- a/AoC2022/04/makefile
+++ b/AoC2022/04/makefile
@@ -12,3 +12,4 @@ run:
 	sbcl --load ~/.sbclrc --script solver.lisp
 	emacs -batch -l ert -l solver.el -f ert-run-tests-batch-and-exit
 	rustc solver.rs && ./solver
+	elixir solver.ex
diff --git a/AoC2022/04/solver.ex b/AoC2022/04/solver.ex
new file mode 100644
index 0000000..0478795
--- /dev/null
+++ b/AoC2022/04/solver.ex
@@ -0,0 +1,36 @@
+defmodule Solver do
+  def to_interval(range) do
+    [left, right] = String.split(range, "-")
+    {left, ""} = Integer.parse(left)
+    {right, ""} = Integer.parse(right)
+    {left, right}
+  end
+
+  def contained({a0, a1}, {b0, b1}) do
+    (a0 - b0) * (a1 - b1) <= 0
+  end
+
+  def overlap({a0, a1}, {b0, b1}) do
+    a0 <= b1 && b0 <= a1
+  end
+end
+
+{:ok, input} = File.read("input")
+
+parsed =
+  input
+  |> String.split("\n", trim: true)
+  |> Enum.map(&String.split(&1, ","))
+  |> Enum.map(fn [left, right] -> {Solver.to_interval(left), Solver.to_interval(right)} end)
+
+parsed
+|> Enum.map(fn {left, right} -> Solver.contained(left, right) end)
+|> Enum.filter(& &1)
+|> length
+|> IO.puts()
+
+parsed
+|> Enum.map(fn {left, right} -> Solver.overlap(left, right) end)
+|> Enum.filter(& &1)
+|> length
+|> IO.puts()