You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
44 lines
1.6 KiB
44 lines
1.6 KiB
-module(day13).
|
|
|
|
-export([solve/1]).
|
|
|
|
-compile(export_all).
|
|
|
|
solve(Input) ->
|
|
PacketPairs = binary:split(Input, <<"\n\n">>, [global, trim_all]),
|
|
Part1 = part1(PacketPairs),
|
|
{Part1, none}.
|
|
|
|
part1(PacketPairs) -> part1(PacketPairs, {1, 0}).
|
|
|
|
part1([], {_Index, Score}) -> Score;
|
|
part1([PacketPair|Rest], {Index, Score}) ->
|
|
[LeftStr, RightStr] = binary:split(PacketPair, <<$\n>>, [trim_all]),
|
|
Left = parse_packet(LeftStr),
|
|
Right = parse_packet(RightStr),
|
|
NewScore = case compare(Left, Right) of
|
|
true -> Score + Index;
|
|
false -> Score
|
|
end,
|
|
part1(Rest, {Index+1, NewScore}).
|
|
|
|
compare([], []) -> undecided;
|
|
compare([], [_|_Rest]) -> true;
|
|
compare([_|_Rest], []) -> false;
|
|
compare([Left | LeftRest], [Right | RightRest]) when is_list(Left) and is_list(Right) ->
|
|
case compare(Left, Right) of
|
|
undecided -> compare(LeftRest, RightRest);
|
|
Result -> Result
|
|
end;
|
|
compare([Left | _] = Lefts, [Right | RightRest]) when is_list(Left) and is_integer(Right) ->
|
|
compare(Lefts, [[Right] | RightRest]);
|
|
compare([Left | LeftRest], [Right | _] = Rights) when is_integer(Left) and is_list(Right) ->
|
|
compare([[Left] | LeftRest], Rights);
|
|
compare([Value | Left], [Value | Right]) when is_integer(Value) -> compare(Left, Right);
|
|
compare([Left|_], [Right|_]) when is_integer(Left) and is_integer(Right) -> Left < Right;
|
|
compare(Left, Right) when is_integer(Left) and is_integer(Right) -> Left < Right.
|
|
|
|
parse_packet(Packet) ->
|
|
{ok, Tokens, _EndLine} = erl_scan:string(unicode:characters_to_list([Packet,$.])),
|
|
{ok, Parsed} = erl_parse:parse_term(Tokens),
|
|
Parsed.
|