92 lines
2.8 KiB
Elixir
92 lines
2.8 KiB
Elixir
defmodule Day5 do
|
|
def part1(input), do: input |> move_with(&move_9000/3) |> top_crates()
|
|
def part2(input), do: input |> move_with(&move_9001/3) |> top_crates()
|
|
|
|
defp move_with({stacks, procedure}, move) do
|
|
for [number, from_index, to_index] <- procedure, reduce: stacks do
|
|
stacks ->
|
|
{moved_from, moved_to} = move.(number, stacks[from_index], stacks[to_index])
|
|
%{stacks | from_index => moved_from, to_index => moved_to}
|
|
end
|
|
end
|
|
|
|
defp move_9000(0, from, to), do: {from, to}
|
|
defp move_9000(number, [crate | from], to), do: move_9000(number - 1, from, [crate | to])
|
|
|
|
defp move_9001(number, from, to) do
|
|
{moving, moved_from} = Enum.split(from, number)
|
|
{moved_from, moving ++ to}
|
|
end
|
|
|
|
defp top_crates(stacks) do
|
|
stacks
|
|
|> Enum.sort_by(fn {label, _stack} -> label end)
|
|
|> Enum.reduce("", fn {_label, [top | _stack]}, acc -> acc <> top end)
|
|
end
|
|
|
|
def input do
|
|
with [input_filename] <- System.argv(),
|
|
{:ok, input} <- File.read(input_filename) do
|
|
[raw_stacks, raw_procedure] = String.split(input, "\n\n")
|
|
|
|
stacks =
|
|
raw_stacks
|
|
|> String.split("\n")
|
|
|> parse_stacks()
|
|
|> Enum.zip()
|
|
|> Enum.map(fn stack -> stack |> Tuple.to_list() |> Enum.drop_while(&is_nil/1) end)
|
|
|> Enum.with_index()
|
|
|> Map.new(fn {stack, index} -> {index + 1, stack} end)
|
|
|
|
procedure =
|
|
raw_procedure
|
|
|> String.split(["move ", " from ", " to ", "\n"], trim: true)
|
|
|> Enum.map(&String.to_integer/1)
|
|
|> Enum.chunk_every(3)
|
|
|
|
{stacks, procedure}
|
|
else
|
|
_ -> :error
|
|
end
|
|
end
|
|
|
|
defp parse_stacks([_labels_]), do: []
|
|
defp parse_stacks([line | rest]), do: [parse_line(line) | parse_stacks(rest)]
|
|
|
|
defp parse_line(<<"">>), do: []
|
|
defp parse_line(<<" ", rest::binary>>), do: [nil | parse_line(rest)]
|
|
defp parse_line(<<"[", crate::binary-1, "]", rest::binary>>), do: [crate | parse_line(rest)]
|
|
defp parse_line(<<" ", rest::binary>>), do: parse_line(rest)
|
|
|
|
#######################
|
|
# HERE BE BOILERPLATE #
|
|
#######################
|
|
|
|
def run do
|
|
case input() do
|
|
:error -> print_usage()
|
|
input -> run_parts_with_timer(input)
|
|
end
|
|
end
|
|
|
|
defp run_parts_with_timer(input) do
|
|
run_with_timer(1, fn -> part1(input) end)
|
|
run_with_timer(2, fn -> part2(input) end)
|
|
end
|
|
|
|
defp run_with_timer(part, fun) do
|
|
{time, result} = :timer.tc(fun)
|
|
IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
|
|
IO.puts("#{result}\n")
|
|
end
|
|
|
|
defp format_time(μsec) when μsec < 1_000, do: "#{μsec}μs"
|
|
defp format_time(μsec) when μsec < 1_000_000, do: "#{μsec / 1000}ms"
|
|
defp format_time(μsec), do: "#{μsec / 1_000_000}s"
|
|
|
|
defp print_usage do
|
|
IO.puts("Usage: elixir day5.exs input_filename")
|
|
end
|
|
end
|
|
|
|
Day5.run()
|