first 4 days

2/main.ml

@@ -0,0 +1,70 @@
+open Printf;;
+open String;;
+
+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 is_not_empty lst = 
+  match lst with
+  | [] -> false 
+  | _  -> true
+
+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 () =
+  let f = open_in "input.txt" in
+  let lines = list_of_lines f in
+  let diffs = List.map (fun a -> int_list_diff @@ parse_int_list a) lines in
+  (* List.iter (fun a -> List.iter (printf "%d, ") a; printf "\n") diffs *)
+  let count = List.fold_left (fun acc l -> if list_diffs_safe l then acc + 1 else acc) 0 diffs in
+  let count2 = List.fold_left (fun acc l -> if list_diff_safe_with_tolerance l then acc + 1 else acc) 0 diffs in
+  printf "%d\n" count;
+  printf "%d\n" count2