110 lines
2.8 KiB
Elixir
110 lines
2.8 KiB
Elixir
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defmodule AOC.Day18 do
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use AOC.Day, day: 18
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def parse_input(lines) do
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Enum.map(lines, fn line ->
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%{"direction" => direction, "length" => length, "color" => color} =
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Regex.named_captures(
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~r/^(?<direction>[UDLR]) (?<length>\d+) \(\#(?<color>[[:alnum:]]+)\)$/,
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line
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)
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{String.to_atom(direction), String.to_integer(length), color}
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end)
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end
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def dig_stretch({y, x}, direction, length) do
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Enum.map(1..length, fn n ->
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case direction do
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:U -> {y - n, x}
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:R -> {y, x + n}
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:D -> {y + n, x}
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:L -> {y, x - n}
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end
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end)
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end
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def execute_dig_plan(dig_plan) do
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Enum.reduce(dig_plan, {%{{0, 0} => true}, {0, 0}}, fn {direction, length, _color},
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{terrain, position} ->
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stretch = dig_stretch(position, direction, length)
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terrain =
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Enum.reduce(stretch, terrain, fn new_position, acc ->
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Map.put(acc, new_position, true)
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end)
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new_position = stretch |> Enum.reverse() |> hd()
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{terrain, new_position}
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end)
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end
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def print_terrain(terrain) do
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max_y = terrain |> Enum.map(&elem(&1, 0)) |> Enum.map(&elem(&1, 0)) |> Enum.max()
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max_x = terrain |> Enum.map(&elem(&1, 0)) |> Enum.map(&elem(&1, 1)) |> Enum.max()
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min_y = terrain |> Enum.map(&elem(&1, 0)) |> Enum.map(&elem(&1, 0)) |> Enum.min()
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min_x = terrain |> Enum.map(&elem(&1, 0)) |> Enum.map(&elem(&1, 1)) |> Enum.min()
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Enum.each(min_y..max_y, fn y ->
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Enum.map(min_x..max_x, fn x ->
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case Map.fetch(terrain, {y, x}) do
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:error -> "."
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_ -> "#"
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end
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end)
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|> Enum.join()
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|> IO.puts()
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end)
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end
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def find_interior_space(terrain) do
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max_x = terrain |> Enum.map(&elem(&1, 0)) |> Enum.map(&elem(&1, 1)) |> Enum.max()
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min_x = terrain |> Enum.map(&elem(&1, 0)) |> Enum.map(&elem(&1, 1)) |> Enum.min()
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edge_x =
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Enum.find(min_x..max_x, fn x ->
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case Map.fetch(terrain, {2, x}) do
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:error -> false
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_ -> true
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end
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end)
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edge_x + 1
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end
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def flood_fill_terrain(terrain) do
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interior_x = find_interior_space(terrain)
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flood_fill_terrain(terrain, {1, interior_x})
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end
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def flood_fill_terrain(terrain, {y, x}) do
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[{y - 1, x}, {y, x + 1}, {y + 1, x}, {y, x - 1}]
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|> Enum.reduce(terrain, fn next_position, acc ->
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case Map.fetch(acc, next_position) do
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:error ->
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acc
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|> Map.put(next_position, true)
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|> flood_fill_terrain(next_position)
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_ ->
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acc
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end
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end)
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end
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def part1(dig_plan) do
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execute_dig_plan(dig_plan)
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|> elem(0)
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# |> tap(&print_terrain/1)
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|> flood_fill_terrain()
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# |> tap(&print_terrain/1)
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|> Enum.count()
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end
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def part2(_input) do
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"TODO"
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end
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end
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