refactor: moving solutions to libs

AdventOfCode2024/lib/day_01.ml

@@ -0,0 +1,44 @@
+open Scanf
+
+let handle_line line = sscanf line "%d   %d" (fun num1 num2 -> (num1, num2))
+let sort_list l = List.sort compare l
+
+let build_lists lines =
+  let rec loop lines l1 l2 =
+    match lines with
+    | [] -> (l1, l2)
+    | head :: tail ->
+        let num1, num2 = handle_line head in
+        loop tail (l1 @ [ num1 ]) (l2 @ [ num2 ])
+  in
+  loop lines [] [] |> fun (l1, l2) -> (sort_list l1, sort_list l2)
+
+let find_occurances l item =
+  let rec loop l item acc =
+    match l with
+    | [] -> acc
+    | head :: tail ->
+        if head == item then loop tail item (acc + 1) else loop tail item acc
+  in
+  loop l item 0
+
+let solve lines =
+  let rec distance l1 l2 acc =
+    match (l1, l2) with
+    | [], [] -> acc
+    | h1 :: t1, h2 :: t2 ->
+        distance t1 t2 (acc + if h1 > h2 then h1 - h2 else h2 - h1)
+    | _, _ -> acc
+  in
+
+  let l1, l2 = build_lists lines in
+  let part1 = distance l1 l2 0 in
+
+  let rec similarity l1 l2 acc =
+    match l1 with
+    | [] -> acc
+    | head :: tail -> similarity tail l2 (acc + (head * find_occurances l2 head))
+  in
+
+  let part2 = similarity l1 l2 0 in
+  (part1, part2)