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