3 files changed, 39 insertions, 0 deletions
diff --git a/2024/lean/Main.lean b/2024/lean/Main.lean
new file mode 100644
index 0000000..cb319c4
--- /dev/null
+++ b/2024/lean/Main.lean
@@ -0,0 +1,12 @@
+import Solutions.Day01
+
+def main (args : List String) : IO Unit := do
+  let usage := "usage: lake exe aoc Day⟨num⟩"
+  match args with
+  | ["--help"] | ["help"] =>
+    IO.println usage
+  | [day] =>
+    let input <- IO.FS.readFile s!"../input/{day.toLower}.txt"
+    IO.println <| solution input
+  | _ =>
+    IO.println usage
diff --git a/2024/lean/Solutions/Day01.lean b/2024/lean/Solutions/Day01.lean
new file mode 100644
index 0000000..1a109df
--- /dev/null
+++ b/2024/lean/Solutions/Day01.lean
@@ -0,0 +1,17 @@
+-- Day 1: Historian Hysteria
+
+def solution (input : String) : String :=
+  let input := input.stripSuffix "\n"|>.splitOn "\n"
+  let l1 := input.map <| fun x => x.splitOn "   " |>.get! 0 |>.toInt!
+  let l2 := input.map <| fun x => x.splitOn "   " |>.get! 1 |>.toInt!
+  let p1 :=
+    List.foldl (· + ·) 0 <|
+      List.zipWith (fun a b => (a - b).natAbs) l1.mergeSort l2.mergeSort
+  let p2 :=
+    List.foldl (· + ·) 0 <|
+      List.map (fun a => a * List.count a l2) l1
+  s!"{p1}, {p2}"
+
+-- def main (args : List String) : IO Unit := do
+--   let input <- IO.FS.readFile s!"../input/{args.get! 0|>.toLower}.txt"
+--   IO.println <| solution input
diff --git a/2024/lean/lakefile.toml b/2024/lean/lakefile.toml
new file mode 100644
index 0000000..4030553
--- /dev/null
+++ b/2024/lean/lakefile.toml
@@ -0,0 +1,10 @@
+name = "aoc"
+version = "0.1.0"
+defaultTargets = ["aoc"]
+
+[[lean_exe]]
+name = "aoc"
+root = "Main"
+
+[[lean_lib]]
+name = "Solutions"