Day 1

2 files changed, 44 insertions, 4 deletions

diff --git a/.gitmodules b/.gitmodules
index 0de780d..12c8bea 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: Copyright 2025 Alexandre Jesus <https://adbjesus.com>
+#
+# SPDX-License-Identifier: CC0-1.0
+
 [submodule "data"]
 	path = data
 	url = git@git.adbjesus.com:aoc2025data
diff --git a/lib/day01.ml b/lib/day01.ml
index e1d6457..9a983a6 100644
--- a/lib/day01.ml
+++ b/lib/day01.ml
@@ -4,8 +4,44 @@
  * SPDX-License-Identifier: GPL-3.0-or-later
  *)
 
-let part1 _ch =
-  failwith "Unimplemented"
+let parse_rotation s =
+  let num = lazy (int_of_string (String.sub s 1 ((String.length s) - 1))) in
+  match s.[0] with
+  | 'R' -> Lazy.force num
+  | 'L' -> -(Lazy.force num)
+  | s -> failwith (Printf.sprintf "Unknown rotation %c" s)
 
-let part2 _ch =
-  failwith "Unimplemented"
+let parse_rotations ch =
+  In_channel.input_all ch
+  |> String.trim
+  |> String.split_on_char '\n'
+  |> List.map parse_rotation
+
+let part1 ch =
+  let m = 100 in
+  let s = 50 in
+  parse_rotations ch
+  |> List.fold_left
+       (fun (a, p) r ->
+         let nxt = (p + r) mod m in
+         let inc = if nxt = 0 then 1 else 0 in
+         (a + inc, nxt)
+       )
+       (0, s)
+  |> fst
+  |> Printf.printf "%d\n"
+
+let part2 ch =
+  let m = 100 in
+  let s = 50 in
+  parse_rotations ch
+  |> List.fold_left
+       (fun (a, p) r ->
+         let nxt = p + r in
+         let inc = (abs nxt) / m + if p > 0 && nxt <= 0 then 1 else 0 in
+         let nxt = ((nxt mod m) + m) mod m in
+         (a + inc, nxt)
+       )
+       (0, s)
+  |> fst
+  |> Printf.printf "%d\n"