first 4 days

4/main.ml

@@ -0,0 +1,160 @@
+open Printf;;
+open Buffer;;
+open String;;
+open Str;;
+
+let rec list_of_lines in_file =
+  try
+    let line = input_line in_file in
+    line :: list_of_lines(in_file)
+  with End_of_file ->
+    close_in in_file;
+    []
+
+let file_to_2d_array in_file =
+  let lines = list_of_lines in_file in
+  let size_x = length @@ List.hd lines in
+  let size_y = List.length lines in
+  let arr = Array.make_matrix size_x size_y '?' in
+  List.iteri (fun j line -> String.iteri (fun i c -> arr.(j).(i) <- c) line) lines;
+  arr
+
+let rec parse_int_list str =
+  let list1 = (List.filter (fun a -> length a != 0) (String.split_on_char ' ' str)) in
+  List.map int_of_string list1
+
+let rec int_list_diff int_list =
+  match int_list with
+  | e1 :: e2 :: tail -> e2 - e1 :: int_list_diff (e2 :: tail)
+  | _ -> []
+
+let list_diffs_safe diff_list =
+  match diff_list with
+  | n :: tail ->
+    if n > 0 then
+      List.for_all (fun x -> x >= 1 && x <= 3) diff_list
+    else if n < 0 then
+      List.for_all (fun x -> x >= -3 && x <= -1) diff_list
+    else
+      false
+  | _ -> true
+
+let rec list_diff_safe_with_tolerance_inner last condition tol diff_list =
+  match diff_list with
+  | x :: tail ->
+    if condition x then
+      list_diff_safe_with_tolerance_inner x condition tol tail
+    else if tol then
+      match tail with
+      | x2 :: tail2 ->
+        list_diff_safe_with_tolerance_inner 0 condition false (x + x2 :: tail2)
+        || list_diff_safe_with_tolerance_inner 0 condition false (last + x :: tail)
+      | _ -> true
+    else
+      false
+  | _ -> true
+
+let list_diff_safe_with_tolerance diff_list =
+  if list_diff_safe_with_tolerance_inner 0 (fun x -> x >= 1 && x <= 3) true diff_list
+  || list_diff_safe_with_tolerance_inner 0 (fun x -> x >= -3 && x <= -1) true diff_list then
+    true
+  else
+    match diff_list with
+    | _ :: tail -> list_diffs_safe tail
+    | _ -> true
+
+let rec count_in_string_inner re str pos acc =
+  try
+    let new_pos = Str.search_forward re str pos in
+    count_in_string_inner re str (new_pos + 1) (acc + 1)
+  with Not_found -> acc
+
+let count_in_string str =
+  let re = Str.regexp "XMAS\\|SAMX" in
+  count_in_string_inner re str 0 0
+
+let prepare_horizontal_str arr =
+  let buf = Buffer.create 1024 in
+  Array.iter (fun row -> Array.iter (fun c -> Buffer.add_char buf c) row; Buffer.add_char buf '\n') arr;
+  Buffer.contents buf
+
+let prepare_vertical_str arr =
+  let buf = Buffer.create 1024 in
+  Seq.iter (fun i -> Array.iter (fun row -> Buffer.add_char buf row.(i)) arr; Buffer.add_char buf '\n')
+    (Seq.init (Array.length arr.(0)) (fun x -> x));
+  Buffer.contents buf
+
+let rec traverse_diagonal fn arr x y  =
+  try
+    let () = fn arr.(y).(x) in
+    traverse_diagonal fn arr (x + 1) (y + 1)
+  with Invalid_argument _ -> ()
+
+let rec traverse_antidiagonal fn arr x y  =
+  try
+    let () = fn arr.(y).(x) in
+    traverse_antidiagonal fn arr (x - 1) (y + 1)
+  with Invalid_argument _ -> ()
+
+let range start stop =
+  Seq.init (stop - start) (fun x -> start + x)
+
+let range_rev start stop =
+  Seq.init (stop - start) (fun x -> stop - 1 - x)
+
+let prepare_diagonal_str arr =
+  let buf = Buffer.create 1024 in
+  let length_x = Array.length arr.(0) in
+  let length_y = Array.length arr in
+  Seq.iter (fun y -> traverse_diagonal (Buffer.add_char buf) arr 0 y; Buffer.add_char buf '\n')
+    (range_rev 1 (length_y - 1));
+  Seq.iter (fun x -> traverse_diagonal (Buffer.add_char buf) arr x 0; Buffer.add_char buf '\n')
+    (range 0 length_x);
+  Buffer.contents buf
+
+let prepare_antidiagonal_str arr =
+  let buf = Buffer.create 1024 in
+  let length_x = Array.length arr.(0) in
+  let length_y = Array.length arr in
+  Seq.iter (fun x -> traverse_antidiagonal (Buffer.add_char buf) arr x 0; Buffer.add_char buf '\n')
+    (range 0 length_x);
+  Seq.iter (fun y -> traverse_antidiagonal (Buffer.add_char buf) arr (length_x - 1) y; Buffer.add_char buf '\n')
+    (range 1 (length_y - 1));
+  Buffer.contents buf
+
+let is_mas_x arr x y =
+  if arr.(y).(x) = 'A' then
+    let nw = arr.(y - 1).(x - 1) in
+    let se = arr.(y + 1).(x + 1) in
+    if (nw = 'M' && se = 'S') || (nw = 'S' && se = 'M') then
+      let ne = arr.(y - 1).(x + 1) in
+      let sw = arr.(y + 1).(x - 1) in
+      (ne = 'M' && sw = 'S') || (ne = 'S' && sw = 'M')
+    else
+      false
+  else
+    false
+
+let count_mas_x arr =
+  let length_x = Array.length arr.(0) in
+  let length_y = Array.length arr in
+  Seq.fold_left 
+    (fun acc y -> acc +
+      Seq.fold_left 
+        (fun acc x -> acc +
+          if is_mas_x arr x y then 1 else 0)
+        0 (range 1 (length_x - 1)))
+    0 (range 1 (length_y - 1))
+
+let () =
+  let f = open_in "input.txt" in
+  let arr = file_to_2d_array f in
+  (* Array.iter (fun x -> Array.iter print_char x; print_newline()) arr;*)
+  let counter = 
+    (count_in_string @@ prepare_horizontal_str arr)
+    + (count_in_string @@ prepare_vertical_str arr)
+    + (count_in_string @@ prepare_diagonal_str arr)
+    + (count_in_string @@ prepare_antidiagonal_str arr) in
+  let counter2 = count_mas_x arr in
+  printf "%d\n" counter;
+  printf "%d\n" counter2