From 4c3a50166bf0f78ce89459c352cc1c6536a8b96d Mon Sep 17 00:00:00 2001
From: DJ O'Leary <dijitol@proton.me>
Date: Sat, 29 Nov 2025 20:23:02 +0100
Subject: chore: make language folders snake_case

---
 2024/ocaml/lib/day_01/part_01.ml  | 40 ++++++++++++++++++
 2024/ocaml/lib/day_01/part_02.ml  | 44 ++++++++++++++++++++
 2024/ocaml/lib/day_02/part_01.ml  | 42 +++++++++++++++++++
 2024/ocaml/lib/day_03/part_01.ml  | 33 +++++++++++++++
 2024/ocaml/lib/day_04/part_01.ml  | 85 +++++++++++++++++++++++++++++++++++++++
 2024/ocaml/lib/day_05/part_01.ml  | 62 ++++++++++++++++++++++++++++
 2024/ocaml/lib/dune               |  5 +++
 2024/ocaml/lib/file/read_input.ml | 11 +++++
 2024/ocaml/lib/grid/cell.ml       | 18 +++++++++
 2024/ocaml/lib/grid/cell.mli      | 18 +++++++++
 2024/ocaml/lib/grid/grid.ml       | 14 +++++++
 2024/ocaml/lib/grid/grid.mli      |  6 +++
 12 files changed, 378 insertions(+)
 create mode 100644 2024/ocaml/lib/day_01/part_01.ml
 create mode 100644 2024/ocaml/lib/day_01/part_02.ml
 create mode 100644 2024/ocaml/lib/day_02/part_01.ml
 create mode 100644 2024/ocaml/lib/day_03/part_01.ml
 create mode 100644 2024/ocaml/lib/day_04/part_01.ml
 create mode 100644 2024/ocaml/lib/day_05/part_01.ml
 create mode 100644 2024/ocaml/lib/dune
 create mode 100644 2024/ocaml/lib/file/read_input.ml
 create mode 100644 2024/ocaml/lib/grid/cell.ml
 create mode 100644 2024/ocaml/lib/grid/cell.mli
 create mode 100644 2024/ocaml/lib/grid/grid.ml
 create mode 100644 2024/ocaml/lib/grid/grid.mli

(limited to '2024/ocaml/lib')

diff --git a/2024/ocaml/lib/day_01/part_01.ml b/2024/ocaml/lib/day_01/part_01.ml
new file mode 100644
index 0000000..100b12a
--- /dev/null
+++ b/2024/ocaml/lib/day_01/part_01.ml
@@ -0,0 +1,40 @@
+(* Day 1: Part 1 *)
+
+let calculate_distance x y = Stdlib.abs (x - y)
+
+(** Require: left and right to be the same length *)
+let solve left right =
+  let sorted_left = List.sort Stdlib.compare left in
+  let sorted_right = List.sort Stdlib.compare right in
+  let distances = List.map2 calculate_distance sorted_left sorted_right in
+  List.fold_left ( + ) 0 distances
+
+let left line =
+  let pos = 0 in
+  let len = String.index line ' ' in
+  String.sub line pos len
+
+let right line =
+  let pos = String.rindex line ' ' + 1 in
+  let len = String.length line - pos in
+  String.sub line pos len
+
+let line_to_tuple line = (left line, right line)
+
+let lines_to_lists lines =
+  let tuples = List.map line_to_tuple lines in
+  let left =
+    List.map
+      (fun t ->
+        let l, _ = t in
+        int_of_string l)
+      tuples
+  in
+  let right =
+    List.map
+      (fun t ->
+        let _, r = t in
+        int_of_string r)
+      tuples
+  in
+  (left, right)
diff --git a/2024/ocaml/lib/day_01/part_02.ml b/2024/ocaml/lib/day_01/part_02.ml
new file mode 100644
index 0000000..25c8b7d
--- /dev/null
+++ b/2024/ocaml/lib/day_01/part_02.ml
@@ -0,0 +1,44 @@
+(* Day 1: Part 2 *)
+
+let rec count_occurrances_help element acc lst =
+  match lst with
+  | [] -> acc
+  | h :: t ->
+      if h = element then count_occurrances_help element (acc + 1) t
+      else count_occurrances_help element acc t
+
+let count_occurrances element lst = count_occurrances_help element 0 lst
+
+let solve left right =
+  List.map (fun x -> x * count_occurrances x right) left
+  |> List.fold_left ( + ) 0
+
+let left line =
+  let pos = 0 in
+  let len = String.index line ' ' in
+  String.sub line pos len
+
+let right line =
+  let pos = String.rindex line ' ' + 1 in
+  let len = String.length line - pos in
+  String.sub line pos len
+
+let line_to_tuple line = (left line, right line)
+
+let lines_to_lists lines =
+  let tuples = List.map line_to_tuple lines in
+  let left =
+    List.map
+      (fun t ->
+        let l, _ = t in
+        int_of_string l)
+      tuples
+  in
+  let right =
+    List.map
+      (fun t ->
+        let _, r = t in
+        int_of_string r)
+      tuples
+  in
+  (left, right)
diff --git a/2024/ocaml/lib/day_02/part_01.ml b/2024/ocaml/lib/day_02/part_01.ml
new file mode 100644
index 0000000..32d7ab8
--- /dev/null
+++ b/2024/ocaml/lib/day_02/part_01.ml
@@ -0,0 +1,42 @@
+(* Day 2: Part 1 *)
+
+type level = int
+type reports = level list list
+
+let rec compare_report_levels_helper comparison prev report =
+  match report with
+  | [] -> true
+  | h :: t -> comparison prev h && compare_report_levels_helper comparison h t
+
+let compare_report_levels comparison report =
+  match report with
+  | [] -> true
+  | h :: t -> compare_report_levels_helper comparison h t
+
+let all_increasing report = compare_report_levels ( < ) report
+let all_decreasing report = compare_report_levels ( > ) report
+
+let at_least_one report =
+  compare_report_levels (fun prev curr -> prev <> curr) report
+
+let at_most_three report =
+  compare_report_levels (fun prev curr -> abs (prev - curr) <= 3) report
+
+let check_report_safety report =
+  if not (all_increasing report || all_decreasing report) then false
+  else if not (at_least_one report && at_most_three report) then false
+  else true
+
+let rec count_safe_reports acc lst =
+  match lst with
+  | [] -> acc
+  | h :: t ->
+      if h then count_safe_reports (acc + 1) t else count_safe_reports acc t
+
+let solve reports =
+  reports |> List.map check_report_safety |> count_safe_reports 0
+
+let line_to_report line =
+  line |> String.split_on_char ' ' |> List.map int_of_string
+
+let lines_to_reports lines = List.map line_to_report lines
diff --git a/2024/ocaml/lib/day_03/part_01.ml b/2024/ocaml/lib/day_03/part_01.ml
new file mode 100644
index 0000000..c12b68a
--- /dev/null
+++ b/2024/ocaml/lib/day_03/part_01.ml
@@ -0,0 +1,33 @@
+(* Day 3: Part 1 *)
+
+let find_mul text =
+  let regex_or_err = Re2.create "mul\\(([0-9]{1,3}),([0-9]{1,3})\\)" in
+  match regex_or_err with
+  | Ok regex -> (
+      let matches = Re2.get_matches regex text in
+      match matches with Ok matches -> matches | Error _ -> [])
+  | Error _ -> []
+
+let extract_pairs (matches : Re2.Match.t list) : (int * int) list =
+  List.map
+    (fun x ->
+      let left = Re2.Match.get x ~sub:(`Index 1) in
+      match left with
+      | None -> (0, 0)
+      | Some left -> (
+          let left_num = int_of_string left in
+          let right = Re2.Match.get x ~sub:(`Index 2) in
+          match right with
+          | None -> (0, 0)
+          | Some right ->
+              let right_num = int_of_string right in
+              (left_num, right_num)))
+    matches
+
+let solve input =
+  input |> find_mul |> extract_pairs
+  |> List.fold_left
+       (fun acc pair ->
+         let left, right = pair in
+         acc + (left * right))
+       0
diff --git a/2024/ocaml/lib/day_04/part_01.ml b/2024/ocaml/lib/day_04/part_01.ml
new file mode 100644
index 0000000..acb3e3b
--- /dev/null
+++ b/2024/ocaml/lib/day_04/part_01.ml
@@ -0,0 +1,85 @@
+(* Day 4: Part 1 *)
+
+type character = { index : int; character : char }
+type direction = N | NE | E | SE | S | SW | W | NW
+
+let all_directions = [ N; NE; E; SE; S; SW; W; NW ]
+let needle = "XMAS"
+
+(** [calculate_row_offset lines] is the offset used to move between the rows of
+    the concatenated variant of [lines] as though it were a grid. Requires:
+    values of [lines] all have the same length *)
+let calculate_row_offset lines =
+  match lines with [] -> 0 | h :: _ -> String.length h
+
+let join_lines lines =
+  let concat_trim acc line = acc ^ String.trim line in
+  List.fold_left concat_trim "" lines
+
+let explode s = List.init (String.length s) (String.get s)
+let is_in_bounds length index = index >= 0 && index < length
+
+let get_at_index line index =
+  let length = String.length line in
+  if not (is_in_bounds length index) then "."
+  else
+    let character = String.get line index in
+    Char.escaped character
+
+let get_direction_index row_offset direction index =
+  match direction with
+  | N -> index - row_offset
+  | NE -> index - row_offset + 1
+  | E -> index + 1
+  | SE -> index + row_offset + 1
+  | S -> index + row_offset
+  | SW -> index + row_offset - 1
+  | W -> index - 1
+  | NW -> index - row_offset - 1
+
+let get_direction_string get_char get_offset_index index =
+  let first = get_char index in
+  let second_index = get_offset_index index in
+  let second = get_char second_index in
+  let third_index = get_offset_index second_index in
+  let third = get_char third_index in
+  let fourth_index = get_offset_index third_index in
+  let fourth = get_char fourth_index in
+  first ^ second ^ third ^ fourth
+
+let check_direction get_from_line get_offset_index index direction =
+  get_direction_string get_from_line (get_offset_index direction) index = needle
+
+let calculate_num_of_matches line row_offset character =
+  let get_from_line_at_index = get_at_index line in
+  let get_offset_direction_index = get_direction_index row_offset in
+  let check_direction_from_index =
+    check_direction get_from_line_at_index get_offset_direction_index
+      character.index
+  in
+  all_directions
+  |> List.map check_direction_from_index
+  |> List.map (fun x -> match x with true -> 1 | false -> 0)
+  |> List.fold_left ( + ) 0
+
+(* Tried:
+   2544 -> too high
+   1272 (previous halved) -> too low *)
+let solve lines =
+  let row_offset = calculate_row_offset lines in
+  let line = join_lines lines in
+  let chars = explode line in
+  let characters = List.mapi (fun i c -> { index = i; character = c }) chars in
+  let xs =
+    List.filter
+      (fun c -> match c.character with 'X' -> true | _ -> false)
+      characters
+  in
+  let calculate_num_of_surrounding_matches_in_line =
+    calculate_num_of_matches line row_offset
+  in
+  let num_of_matches =
+    List.map calculate_num_of_surrounding_matches_in_line xs
+    |> List.fold_left ( + ) 0
+  in
+  num_of_matches
diff --git a/2024/ocaml/lib/day_05/part_01.ml b/2024/ocaml/lib/day_05/part_01.ml
new file mode 100644
index 0000000..f32bef1
--- /dev/null
+++ b/2024/ocaml/lib/day_05/part_01.ml
@@ -0,0 +1,62 @@
+(* Day 5: Part 1 *)
+
+module StringMap = Map.Make (String)
+
+let inverse_page_rule page_rule =
+  String.split_on_char '|' page_rule |> fun lst ->
+  match lst with [] -> "" | _ :: _ -> String.concat "|" (List.rev lst)
+
+(** [parse_aux acc page_rules] is a map of all invalid transitions as defined by
+    [page_rules] *)
+let rec get_invalid_transitions_aux acc page_rules : unit StringMap.t =
+  match page_rules with
+  | [] -> acc
+  | h :: t ->
+      get_invalid_transitions_aux
+        (acc |> StringMap.add (inverse_page_rule h) ())
+        t
+
+let get_invalid_transitions page_rules =
+  get_invalid_transitions_aux StringMap.empty page_rules
+
+(** [solve page_rules updates] is the solution for this puzzle, given the
+    [page_rules] and a list of [updates].
+
+    BELOW DOESN'T WORK: no guarantee that second page comes immediately after
+    the first
+    - pass in updates to solve
+    - make sliding window of 2 elements
+    - invert element order and concat
+    - check if key is in map from [parse page_rules],
+    - if yes, then it is an illegal transition
+    - if no, then add the list to a list for further processing *)
+let solve page_rules _ =
+  let invalid_transitions = get_invalid_transitions page_rules in
+  ()
+
+let _ =
+  solve
+    [
+      "47|53";
+      "97|13";
+      "97|61";
+      "97|47";
+      "75|29";
+      "61|13";
+      "75|53";
+      "29|13";
+      "97|29";
+      "53|29";
+      "61|53";
+      "97|53";
+      "61|29";
+      "47|13";
+      "75|47";
+      "97|75";
+      "47|61";
+      "75|61";
+      "47|29";
+      "75|13";
+      "53|13";
+    ]
+    []
diff --git a/2024/ocaml/lib/dune b/2024/ocaml/lib/dune
new file mode 100644
index 0000000..84e62ca
--- /dev/null
+++ b/2024/ocaml/lib/dune
@@ -0,0 +1,5 @@
+(library
+ (name AoC_2024)
+ (libraries re2))
+
+(include_subdirs qualified)
diff --git a/2024/ocaml/lib/file/read_input.ml b/2024/ocaml/lib/file/read_input.ml
new file mode 100644
index 0000000..0f7470b
--- /dev/null
+++ b/2024/ocaml/lib/file/read_input.ml
@@ -0,0 +1,11 @@
+let rec lines_from_channel ic =
+  try
+    let line = input_line ic in
+    line :: lines_from_channel ic
+  with End_of_file -> []
+
+let lines_from_file filename =
+  let channel = open_in filename in
+  let lines = lines_from_channel channel in
+  close_in channel;
+  lines
diff --git a/2024/ocaml/lib/grid/cell.ml b/2024/ocaml/lib/grid/cell.ml
new file mode 100644
index 0000000..186e451
--- /dev/null
+++ b/2024/ocaml/lib/grid/cell.ml
@@ -0,0 +1,18 @@
+type t = {
+  value : string;
+  up : t option;
+  down : t option;
+  left : t option;
+  right : t option;
+}
+
+let create value = { value; up = None; down = None; left = None; right = None }
+let with_up up c = { c with up = Some up }
+let with_down down c = { c with down = Some down }
+let with_left left c = { c with left = Some left }
+let with_right right c = { c with right = Some right }
+let move_up co = match co with Some c -> c.up | None -> None
+let move_down co = match co with Some c -> c.down | None -> None
+let move_left co = match co with Some c -> c.left | None -> None
+let move_right co = match co with Some c -> c.right | None -> None
+let ( = ) c1 c2 = c1.value = c2.value
diff --git a/2024/ocaml/lib/grid/cell.mli b/2024/ocaml/lib/grid/cell.mli
new file mode 100644
index 0000000..e61e34a
--- /dev/null
+++ b/2024/ocaml/lib/grid/cell.mli
@@ -0,0 +1,18 @@
+type t = {
+  value : string;
+  up : t option;
+  down : t option;
+  left : t option;
+  right : t option;
+}
+
+val create : string -> t
+val with_up : t -> t -> t
+val with_down : t -> t -> t
+val with_left : t -> t -> t
+val with_right : t -> t -> t
+val move_up : t option -> t option
+val move_down : t option -> t option
+val move_left : t option -> t option
+val move_right : t option -> t option
+val ( = ) : t -> t -> bool
diff --git a/2024/ocaml/lib/grid/grid.ml b/2024/ocaml/lib/grid/grid.ml
new file mode 100644
index 0000000..0d6bc4c
--- /dev/null
+++ b/2024/ocaml/lib/grid/grid.ml
@@ -0,0 +1,14 @@
+let rec to_grid_aux tokens max_width acc =
+  match tokens with
+  | [] -> acc
+  | h :: t ->
+      let new_cell = Cell.create h |> Cell.with_left acc in
+      let new_acc = acc |> Cell.with_right new_cell in
+      to_grid_aux t max_width new_acc
+
+let to_grid tokens max_width : Cell.t option =
+  match tokens with
+  | [] -> None
+  | h :: t ->
+      let first_cell = Cell.create h in
+      Some (to_grid_aux t max_width first_cell)
diff --git a/2024/ocaml/lib/grid/grid.mli b/2024/ocaml/lib/grid/grid.mli
new file mode 100644
index 0000000..a69fcfe
--- /dev/null
+++ b/2024/ocaml/lib/grid/grid.mli
@@ -0,0 +1,6 @@
+val to_grid : string list -> int -> Cell.t option
+(** The cell in the top left corner of the grid is returned where each element
+    of [tokens] is converted into rows with [width]. An empty list of [tokens]
+    returns None. Requires: [width] is greater than 0 **)
+
+(* val print : Cell.t -> () *)
-- 
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