Day 3!

.gitignore

@@ -2,3 +2,4 @@
 ./zig-cache
 _build
 *.txt
+dune.lock

AdventOfCode2024/AdventOfCode2024.opam

@@ -12,6 +12,7 @@ bug-reports: "https://github.com/username/reponame/issues"
 depends: [
   "ocaml"
   "dune" {>= "3.16"}
+  "re2"
   "odoc" {with-doc}
 ]
 build: [

AdventOfCode2024/bin/main.ml

@@ -13,7 +13,7 @@ let read_lines name =
 let () =
   print_endline "\nAdvent of Code 2024";
   let part1, part2 =
-    read_lines "./inputs/02.txt" |> AdventOfCode2024.Day_02.solve
+    read_lines "./inputs/03.txt" |> AdventOfCode2024.Day_03.solve
   in
   Printf.printf "Part 1: %s\nPart 2: %s\n" (string_of_int part1)
     (string_of_int part2)

AdventOfCode2024/dune-project

@@ -19,7 +19,7 @@
  (name AdventOfCode2024)
  (synopsis "A short synopsis")
  (description "A longer description")
- (depends ocaml dune)
+ (depends ocaml dune re2)
  (tags
   (topics "to describe" your project)))
 

AdventOfCode2024/lib/day_03.ml

@@ -0,0 +1,117 @@
+let rec print_list l =
+  match l with
+  | [] -> print_endline ""
+  | head :: tail ->
+      print_int head;
+      print_string " | ";
+      print_list tail
+
+let rec print_s_list l =
+  match l with
+  | [] -> print_endline ""
+  | head :: tail ->
+      print_string head;
+      print_string " | ";
+      print_s_list tail
+
+let rec print_tuple_list l =
+  match l with
+  | [] -> print_endline ""
+  | (index, value) :: tail ->
+      print_int index;
+      print_string ", ";
+      print_string (string_of_bool value);
+      print_string " | ";
+      print_tuple_list tail
+
+let get_toggle_positions line =
+  let toggle_on_regex = Re2.create_exn {|do\(\)|} in
+  let toggle_off_regex = Re2.create_exn {|don't\(\)|} in
+  let on_matches = Re2.get_matches_exn toggle_on_regex line in
+  let off_matches = Re2.get_matches_exn toggle_off_regex line in
+  let get_indexes =
+    List.fold_left
+      (fun acc i ->
+        let start, _ = Re2.Match.get_pos_exn ~sub:(`Index 0) i in
+        [ start ] @ acc)
+      []
+  in
+
+  let on_indexes = get_indexes on_matches in
+  let off_indexes = get_indexes off_matches in
+  List.sort
+    (fun (i, _) (j, _) -> i - j)
+    ((List.rev on_indexes |> List.map (fun i -> (i, true)))
+    @ (List.rev off_indexes |> List.map (fun i -> (i, false))))
+
+let get_all_numbers_positions line =
+  let instruction_regex = Re2.create_exn {|mul\((\d+),(\d+)\)|} in
+  let matches_indexes = Re2.get_matches_exn instruction_regex line in
+  let indexes =
+    List.fold_left
+      (fun acc i ->
+        let start, _ = Re2.Match.get_pos_exn ~sub:(`Index 0) i in
+        [ start ] @ acc)
+      [] matches_indexes
+  in
+  List.rev indexes
+
+let get_all_numbers line =
+  let instruction_regex = Re2.create_exn {|mul\((\d+),(\d+)\)|} in
+  let matches = Re2.find_all_exn instruction_regex line in
+  let nums =
+    List.fold_left
+      (fun acc m ->
+        let num1, num2 = Scanf.sscanf m "mul(%d,%d)" (fun n1 n2 -> (n1, n2)) in
+        [ (num1, num2) ] @ acc)
+      [] matches
+  in
+  List.rev nums
+
+let get_closest_item l item starting =
+  let rec get_closest_item' l closest item =
+    match l with
+    | [] -> closest
+    | (head, v) :: tail ->
+        if head < item then get_closest_item' tail (head, v) item else closest
+  in
+  get_closest_item' l (0, starting) item
+
+let solve lines =
+  let part1 =
+    List.fold_left
+      (fun acc line ->
+        let line_value =
+          List.fold_left
+            (fun acc (num1, num2) -> acc + (num1 * num2))
+            0 (get_all_numbers line)
+        in
+        acc + line_value)
+      0 lines
+  in
+
+  let part2, _ =
+    List.fold_left
+      (fun (acc, toggle) line ->
+        let mul_indexes = get_all_numbers_positions line in
+        let mul_intructions = get_all_numbers line in
+        let toggles = get_toggle_positions line in
+        let closest_check = get_closest_item toggles in
+
+        let rec loop indexes instructions acc last_toggle =
+          match (indexes, instructions) with
+          | [], [] -> (acc, last_toggle)
+          | head :: tail, (n1, n2) :: in_tail ->
+              let _, is_on = closest_check head toggle in
+
+              let acc' = if is_on then acc + (n1 * n2) else acc in
+              loop tail in_tail acc' is_on
+          | _ -> (acc, last_toggle)
+        in
+
+        let acc', last_toggle = loop mul_indexes mul_intructions 0 toggle in
+        (acc + acc', last_toggle))
+      (0, true) lines
+  in
+
+  (part1, part2)

AdventOfCode2024/lib/dune

@@ -1,2 +1,3 @@
 (library
- (name AdventOfCode2024))
+ (name AdventOfCode2024)
+ (libraries re2))