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|
module Battery : sig
type t
val of_int : int -> t
val to_int : t -> int
val to_string : t -> string
val compare : t -> t -> int
val pp : t -> string
end = struct
type t = int
let of_int i = i
let to_int b = b
let to_string = string_of_int
let compare = Int.compare
let pp = string_of_int
end
module BatteryBank : sig
type t
val highest_joltage : t -> int
val of_string : string -> t
val of_list : Battery.t list -> t
val to_list : t -> Battery.t list
val pp : t -> string
end = struct
type t = Battery.t list
let rec highest_joltage bb =
match highest_joltage_aux (None, None) bb with
| None, None ->
0
| Some x, Some y ->
int_of_string (Battery.to_string x ^ Battery.to_string y)
| _ ->
failwith "highest_joltage_aux must result in two digits"
and highest_joltage_aux acc = function
| [] ->
acc
| h :: t ->
highest_joltage_aux
( match acc with
| None, None ->
(Some h, None)
| Some first, None ->
(Some first, Some h)
| Some first, Some second ->
swap_if_higher first second h (List.length t = 0)
| _ ->
failwith "this branch should be impossible" )
t
and swap_if_higher first second considering is_end =
let c_gt_f = Battery.compare considering first = 1 in
let c_gt_s = Battery.compare considering second = 1 in
let f_gt_s = Battery.compare first second = 1 in
if c_gt_f && c_gt_s && f_gt_s then
if is_end then (Some first, Some considering) else (Some considering, None)
else if (not c_gt_f) && c_gt_s && f_gt_s then (Some first, Some considering)
else if c_gt_f && c_gt_s && not f_gt_s then
if is_end then (Some second, Some considering)
else (Some considering, None)
else if (not c_gt_f) && (not c_gt_s) && f_gt_s then (Some first, Some second)
else if c_gt_f && (not c_gt_s) && not f_gt_s then
(Some second, Some considering)
else (Some first, Some second)
let of_string s =
s |> String.to_seq
|> Seq.map (fun c -> Char.escaped c |> int_of_string |> Battery.of_int)
|> List.of_seq
let of_list lst = lst
let to_list bb = bb
let pp bb =
"[ "
^ ( bb |> List.map Battery.pp
|> List.fold_left
(fun acc b ->
if acc = "" then b ^ ";" else Printf.sprintf "%s %s;" acc b )
"" )
^ " ]"
end
|
