let split s =
    let half = (String.length s) / 2 in
    (String.sub s 0 half, String.sub s half half)

let find_duplicates s1 s2 =
    String.to_seq s1
    |> Seq.filter (fun c -> String.contains s2 c)
    |> Seq.fold_left
        (fun acc c -> if String.contains acc c then acc else acc ^ String.make 1 c)
        ""

let priority item =
    let num = int_of_char item in
    if num > 96 then num - 96
    else num - 38

let find_duplicates3 s1 s2 s3 =
    find_duplicates s1 (find_duplicates s2 s3)

let get_duplicate dup =
    try Some(String.get dup 0 |> priority)
    with Failure _ -> None

open Utils

let part1 l = l
    |> List.filter_map (fun s ->
        split s
        |> uncurry find_duplicates
        |> get_duplicate)
    |> List.fold_left (+) 0 ;;

let triplets l =
    let rec aux res = function
        | [] | [_] | _ :: _ :: []-> res
        | elv1 :: elv2 :: elv3 :: tail -> aux ((elv1, elv2, elv3) :: res) tail in
    aux [] l ;;

let part2 l = l
    |> triplets
    |> List.filter_map (fun triplet ->
        (uncurry3 find_duplicates3) triplet
        |> get_duplicate)
    |> List.fold_left (+) 0 ;;

"\n1: " ^ string_of_int (read_file "bin/d3/input.txt" |> part1) ^
"\n2: " ^ string_of_int (read_file "bin/d3/input.txt" |> part2) |> print_endline