module IntSet = Set_ext.Make(Int) let read_ints = Bracket.infile_lines ~line:int_of_string ~of_seq:IntSet.of_seq let rec find ?(target=2020) ~n set = if n < 1 then raise (Invalid_argument "n must be at least 1") else if n = 1 then if IntSet.mem target set then Some [target] else None else let joined x = Option.map (List.cons x) (find ~target:(target - x) ~n:(n - 1) set) in IntSet.exists_opt joined set let main' n input = match find ~n (read_ints input) with | Some xs -> Misc.print_prod xs | None -> raise Not_found let main = Misc.main 1 [|main' 2; main' 3|] let%expect_test "part 1" = main' 2 "../../data/day1"; (* is this always the right path??? *) [%expect{| 534 * 1486 = 793524 |}] let%expect_test "part 2" = main' 3 "../../data/day1"; [%expect{| 71 * 686 * 1263 = 61515678 |}]