add 2024 day 12
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elixir/livebook/2024/day12.livemd
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elixir/livebook/2024/day12.livemd
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# AOC2024 Day 12
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## Section
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```elixir
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defmodule Grid2D do
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defstruct width: nil, height: nil
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@directions %{
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straight: [
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{1, 0},
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{-1, 0},
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{0, 1},
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{0, -1}
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],
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diagonal: [
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{1, 1},
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{1, -1},
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{-1, 1},
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{-1, -1}
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]
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}
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def new(width, height) do
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%Grid2D{width: width, height: height}
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end
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@doc """
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## Examples
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iex> Grid2D.index_to_coord(Grid2D.new(5,5), 0)
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{0,0}
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iex> Grid2D.index_to_coord(Grid2D.new(5,5), 5)
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{0,1}
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iex> Grid2D.index_to_coord(Grid2D.new(5,5), 6)
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{1,1}
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iex> Grid2D.index_to_coord(Grid2D.new(5,5), 3)
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{3,0}
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iex> Grid2D.index_to_coord(Grid2D.new(5,5), 24)
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{4, 4}
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"""
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def index_to_coord(%Grid2D{width: w}, index) do
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{rem(index, w), floor(index / w)}
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end
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@doc """
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## Examples
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iex> Grid2D.coord_to_index( Grid2D.new(5,5), {0,0})
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0
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iex> Grid2D.coord_to_index( Grid2D.new(5,5), {4,4})
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24
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iex> Grid2D.coord_to_index( Grid2D.new(5,5), {2,2})
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12
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"""
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def coord_to_index(%Grid2D{width: w}, {x, y}) do
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y * w + x
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end
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@doc """
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## Examples
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iex> Grid2D.neighbors({0, 0}, Grid2D.new(5,5)) |> MapSet.new()
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MapSet.new([{0, 1}, {1, 1}, {1,0}])
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iex> Grid2D.neighbors({2, 2}, Grid2D.new(5,5)) |> MapSet.new()
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[{1, 1}, {1, 2}, {1, 3}, {2, 1}, {2, 3}, {3, 1}, {3, 2}, {3, 3}] |> MapSet.new()
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iex> Grid2D.neighbors({4, 4}, Grid2D.new(5,5)) |> MapSet.new
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[{3, 3}, {3, 4}, {4, 3}] |> MapSet.new
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"""
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def neighbors(p, g, allowed_directions \\ :all) do
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directions(allowed_directions)
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|> Stream.map(&add(p, &1))
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|> Stream.filter(&is_in_grid?(&1, g))
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end
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@doc """
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Distance from two points in a grid
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iex> Grid2D.distance(Grid2D.new(5,5), {0,0}, {0,1}, :radial)
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1
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iex> Grid2D.distance(Grid2D.new(5,5), {0,0}, {1,1}, :radial)
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1
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iex> Grid2D.distance(Grid2D.new(5,5), {0,0}, {1,2}, :radial)
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2
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"""
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def distance(grid, p1, p2, type)
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def distance(_, {x, y}, {a, b}, :radial), do: max(abs(x - a), abs(y - b))
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@doc """
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Add two points together pairwise
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iex> Grid2D.add({0,0}, {0,1})
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{0,1}
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iex> Grid2D.add({2,3}, {3,2})
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{5,5}
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"""
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def add({x, y}, {j, k}), do: {x + j, y + k}
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@doc """
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Test if a point is in a grid
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iex> Grid2D.is_in_grid?({1, 2}, %Grid2D{width: 3, height: 4})
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true
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iex> Grid2D.is_in_grid?({2, 2}, %Grid2D{width: 2, height: 4})
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false
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"""
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def is_in_grid?({x, y}, %Grid2D{width: w, height: h}), do: x < w and y < h and x >= 0 and y >= 0
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@spec directions(allowed :: :all | :straight | :diagonal) :: any()
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def directions(allowed \\ :all)
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def directions(:all), do: directions(:straight) ++ directions(:diagonal)
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def directions(:straight), do: @directions |> Map.get(:straight)
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def directions(:diagonal), do: @directions |> Map.get(:diagonal)
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def mul({x, y}, n), do: {n*x, n*y}
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end
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```
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```elixir
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defmodule EnumUtil do
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def pick_n(enum, n)
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def pick_n([], _), do: []
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def pick_n([a | rest], n) do
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pick_n(rest, n, n, []) ++ pick_n(rest, n, n - 1, [a])
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end
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defp pick_n([], n, _, acc) do
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if acc |> Enum.count == n do
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[acc]
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else
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[]
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end
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end
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defp pick_n(_, _, 0, acc), do: [acc]
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defp pick_n([a | rest], n, r, acc) do
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pick_n(rest, n, r, acc) ++ pick_n(rest, n, r - 1, [a | acc])
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end
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end
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```
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```elixir
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input = """
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"""
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```
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```elixir
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lines = input |> String.trim() |> String.split("\n")
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height = lines |> Enum.count
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width = lines |> Enum.at(0) |> String.length()
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tiles = lines |> Stream.with_index() |> Stream.flat_map(fn {line, i} -> line |> String.graphemes() |> Stream.with_index() |> Enum.map(fn {c, j} -> {{j, i}, c} end) end) |> Enum.into(%{})
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grid = Grid2D.new(width, height)
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```
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```elixir
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defmodule Crawl do
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def crawl([], _, _, acc), do: acc
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def crawl(points, tiles, grid, acc) do
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n = points
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|> Enum.flat_map(fn p -> Grid2D.neighbors(p, grid, :straight)
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|> Enum.reject(&(MapSet.member?(acc, &1) or Map.get(tiles, &1) != Map.get(tiles, p))) end)
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|> Enum.uniq()
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# IO.puts("#{inspect(n)}")
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crawl(n, tiles, grid, points |> Enum.reduce(acc, fn x, s -> MapSet.put(s, x) end))
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end
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def crawl(tiles, grid) do
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for {pt, _} <- tiles, reduce: {MapSet.new([]),[]} do
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{seen, list} ->
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if !MapSet.member?(seen, pt) do
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visited = Crawl.crawl([pt], tiles, grid, MapSet.new([pt]))
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{seen |> MapSet.union(visited), [visited | list]}
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else
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{seen, list}
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end
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end |> elem(1)
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end
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def pricep1(regions) do
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for region <- regions, reduce: 0 do
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acc ->
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area = region |> MapSet.size()
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perimeter = 4*area - (region |> MapSet.to_list() |> EnumUtil.pick_n(2) |> Stream.map(
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fn [{a,b},{x,y}] ->
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if (a == x and abs(b-y) == 1) or (b == y and abs(a-x) == 1) do
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2
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else
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0
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end
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end
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) |> Enum.sum())
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acc + area*perimeter
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end
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end
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def rotate90({a, b}), do: {-b, a}
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def pricep2(regions, tiles, grid) do
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for region <- regions, reduce: 0 do
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acc ->
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sides = for direction <- Grid2D.directions(:straight) do
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for tile <- region,
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neighbor = Grid2D.add(tile, direction),
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Map.get(tiles, neighbor) != Map.get(tiles, tile),
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reduce: {MapSet.new, 0} do
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{used, total} ->
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if !MapSet.member?(used, tile) do
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scan_dir = rotate90(direction)
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line = Stream.iterate(1, &(&1 + 1))
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|> Stream.map(fn n ->
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if rem(n, 2) == 0 do
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{:up, div(n,2)}
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else
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{:down, div(n+1, 2)*-1}
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end
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end)
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|> Stream.map(&({elem(&1, 0), Grid2D.mul(scan_dir, elem(&1, 1))}))
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|> Enum.reduce_while(
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%{line: MapSet.new, up: true, down: true},
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fn {dir, next}, %{line: line} = acc ->
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next = Grid2D.add(next, tile)
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is_same? = Map.get(tiles, next) == Map.get(tiles, tile)
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next_external? = Map.get(tiles, Grid2D.add(next, direction)) != Map.get(tiles, next)
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acc = if acc[dir] and Grid2D.is_in_grid?(next, grid) and is_same? and next_external? do
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%{acc | line: MapSet.put(line, next)}
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else
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acc |> Map.put(dir, false)
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end
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{(if acc[:up] or acc[:down], do: :cont, else: :halt), acc}
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end
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) |> Map.get(:line)
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{used |> MapSet.union(line), total + 1}
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else
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{used, total}
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end
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end |> elem(1)
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end |> Enum.sum()
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area = region |> MapSet.size()
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acc + area*sides
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end
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end
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end
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```
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```elixir
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regions = Crawl.crawl(tiles, grid)
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```
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```elixir
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Crawl.pricep1(regions)
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```
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```elixir
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Crawl.pricep2(regions, tiles, grid)
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```
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