This topic is about Day 5 of the Advent of Code 2022 .
Link to our leaderboard:
https://adventofcode.com/2022/leaderboard/private/view/370884
The entry code is:
370884-a6a71927
Good luck!
2 Likes
This time parsing first part of the input seemed more of a challenge than actual problem, so I manually parsed initial state and automated it after submitting answers:
main(File) ->
{ok, RawData} = file:read_file(File),
[RawState, RawMoves] = binary:split(RawData, <<"\n\n">>, [global, trim]),
State = parse_state(RawState),
Data = parse_moves(RawMoves),
io:format("part 1: ~p~n", [solve1(State, Data)]),
io:format("part 2: ~p~n", [solve2(State, Data)]).
parse_state(RawState0) ->
RawState = binary:split(RawState0, <<"\n">>, [global]),
Cols = binary_to_integer(lists:last(binary:split(lists:last(RawState), <<" ">>, [global, trim]))),
Positions = lists:zip(lists:seq(1, Cols), [ 1 + 4 * X || X <- lists:seq(0, Cols - 1) ]),
State = maps:from_list([ {N, [ C || R <- lists:droplast(RawState), (C = pick_byte(R, P)) =/= <<" ">> ]}
|| {N, P} <- Positions ]),
io:format("State: ~p~n", [State]),
State.
pick_byte(Binary, Pos) when byte_size(Binary) >= Pos ->
binary:part(Binary, {Pos, 1});
pick_byte(_Binary, _Pos) ->
<<" ">>.
parse_moves(RawMoves) ->
[ [ binary_to_integer(X)
|| X <- binary:split(N, [<<"move ">>, <<" from ">>, <<" to ">>], [global, trim]), X =/= <<>>]
|| N <- binary:split(RawMoves, <<"\n">>, [global, trim]) ].
solve1(State, Data) ->
top_crates(lists:foldl(fun crane_9000/2, State, Data)).
solve2(State, Data) ->
top_crates(lists:foldl(fun crane_9001/2, State, Data)).
crane_9000(Move, State) ->
crane(Move, State, fun lists:reverse/2).
crane_9001(Move, State) ->
crane(Move, State, fun lists:append/2).
crane([N, From, To], State, AppendFun) ->
FromStack = maps:get(From, State),
ToStack = maps:get(To, State),
{ToPut, NewFromStack} = lists:split(N, FromStack),
State#{To => AppendFun(ToPut, ToStack),
From => NewFromStack}.
top_crates(State) ->
<< <<(hd(X))/binary>> || X <- maps:values(State) >>.
Can’t think of better way to parse initial state at this time of day, I’m sure it’s possible, will check it later
2 Likes
I couldn’t do day 10 with Erlang, but today’s Erlang adventure was with Day 5. I have an observation though (I will google it later). binary_to_list(list_to_binary(["A", "B", "C"])) is "ABC" but ["A", "B", "C"] and "ABC" are not the same. So X != a2z(z2a(X)) here?
Another slight annoying thing for me was that array is 0 indexed whereas lists are 1? As are tuples? But aren’t arrays based on tuples? Looks like I have some learning by learning (instead of doing) to do tomorrow.
Anyways, here’s my day 5 in Erlang:
-module(day_5).
-export([solve/0]).
input() ->
{ok, Data} = file:read_file("data/5.txt"),
Data.
solve() ->
Data = parse(input()),
{solve1(Data), solve2(Data)}.
solve1({State, Steps}) ->
solver({State, Steps}, fun lists:reverse/1).
solve2({State, Steps}) ->
solver({State, Steps}, fun(X) -> X end).
solver({State, Steps}, Fun) ->
Reducer =
fun({Q, S, D}, Acc) ->
Source = array:get(S - 1, Acc),
Destination = array:get(D - 1, Acc),
{Move, NewSource} = lists:split(Q, Source),
NewDestination = Fun(Move) ++ Destination,
array:set(S - 1, NewSource, array:set(D - 1, NewDestination, Acc))
end,
top_containers(array:to_list(
lists:foldl(Reducer, State, Steps))).
parse(Data) ->
[State, Steps] = binary:split(Data, <<"\n\n">>),
{parse_state(State), parse_steps(Steps)}.
parse_steps(Steps) ->
RawSteps = lists:map(fun binary_to_list/1, binary:split(Steps, <<"\n">>, [global])),
ToInteger = fun(X) -> element(1, string:to_integer(X)) end,
[begin
[_, Q, _, S, _, D] = string:split(Step, " ", all),
{ToInteger(Q), ToInteger(S), ToInteger(D)}
end
|| Step <- RawSteps].
parse_state(State) ->
Rows =
[binary_to_list(X)
|| X
<- lists:droplast(
binary:split(remove_brackets(State), <<"\n">>, [global]))],
Containers =
lists:map(fun(X) -> [string:trim(Container) || Container <- string:split(X, " ", all)]
end,
Rows),
array:from_list([lists:dropwhile(fun(X) -> X == [] end, C)
|| C <- common:transpose(Containers)]).
remove_brackets(Container) ->
binary:replace(
binary:replace(Container, <<"[">>, <<" ">>, [global]), <<"]">>, <<" ">>, [global]).
top_containers(Containers) ->
binary_to_list(list_to_binary([hd(X) || X <- Containers])).
2 Likes