fn

2024/day2/main.ml

@@ -20,17 +20,19 @@ let from input =
 ;;
 
 let first data =
-  let rec is_safe_adj = function
+  let is_safe l =
-    | x :: y :: tl -> if Int.abs (x - y) > 2 then true else is_safe_adj (y :: tl)
+    let order l =
-    | _ :: [] | [] -> false
+      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 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
-  let is_safe_order l =
+  List.filter is_safe data |> List.length
-    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 second data =