fn

2024/day2/main.ml

@@ -20,17 +20,19 @@ let from input =
 ;;
 
 let first data =
-  let rec is_safe_adj = function
-    | x :: y :: tl -> if Int.abs (x - y) > 2 then true else is_safe_adj (y :: tl)
-    | _ :: [] | [] -> false
-  in
-  let is_safe_order l =
+  let is_safe l =
+    let order l =
       let sorted = List.fast_sort compare l in
       List.equal (fun a b -> a = b) l sorted
       || List.equal (fun a b -> a = b) l (List.rev sorted)
     in
-  let res = List.filter (fun x -> is_safe_order x && is_safe_adj x) data in
-  List.length res
+    let rec adjacent = function
+      | x :: y :: tl -> if Int.abs (x - y) >= 3 then true else adjacent (y :: tl)
+      | _ :: [] | [] -> false
+    in
+    order l && adjacent l
+  in
+  List.filter is_safe data |> List.length
 ;;
 
 let second data =