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December 8, 2015 00:14
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Advent of Code. Day 6 - Part 2.
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parse_command = fn command -> | |
{cmd, rest} = case command do | |
<<"turn on ", rest :: binary>> -> {:on, rest} | |
<<"turn off ", rest :: binary>> -> {:off, rest} | |
<<"toggle ", rest :: binary>> -> {:toggle, rest} | |
end | |
[x1y1, _, x2y2] = String.split(rest) | |
[x1, y1] = String.split(x1y1, ",") |> Enum.map(&(String.to_integer(&1))) | |
[x2, y2] = String.split(x2y2, ",") |> Enum.map(&(String.to_integer(&1))) | |
{cmd, min(x1, x2), min(y1, y2), max(x1, x2), max(y1, y2) } | |
end | |
generate_coordinates = fn x1, y1, x2, y2 -> | |
Enum.flat_map(x1..x2, fn x -> | |
Enum.map(y1..y2, fn y -> | |
{x, y} | |
end) | |
end) | |
end | |
fill_map = fn map, cmd, x1, y1, x2, y2 -> | |
Enum.reduce(generate_coordinates.(x1, y1, x2, y2), map, fn {x, y}, map -> | |
map = case cmd do | |
:on -> Dict.update(map, {x, y}, 1, &(&1 + 1)) | |
:off -> Dict.update(map, {x, y}, 0, &(if (&1 > 0) do &1 - 1 else &1 end)) | |
:toggle -> Dict.update(map, {x, y}, 2, &(&1 + 2)) | |
end | |
map | |
end) | |
end | |
input_stream = File.stream!("input.txt") | |
final_map = Enum.reduce(input_stream, %{}, fn line, light_map -> | |
{cmd, x1, y1, x2, y2} = parse_command.(line |> String.strip) | |
light_map = fill_map.(light_map, cmd, x1, y1, x2, y2) | |
light_map | |
end) | |
total_brightness = Enum.reduce(final_map, 0, fn {_, brightness}, acc -> | |
acc + brightness | |
end) | |
IO.puts "Total brightness: #{total_brightness}" |
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