105 lines
2.3 KiB
Elixir
105 lines
2.3 KiB
Elixir
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import AOC
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aoc 2021, 20 do
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import Integer, only: [is_even: 1]
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def p1 do
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{algorithm, source_image} = input()
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enhance(source_image, algorithm, 2)
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|> Map.values()
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|> Enum.count(&(&1))
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end
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def p2 do
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{algorithm, source_image} = input()
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enhance(source_image, algorithm, 50)
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|> Map.values()
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|> Enum.count(&(&1))
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end
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def enhance(image, algorithm, to_iteration, iteration \\ 0)
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def enhance(image, _algorithm, iteration, iteration), do: image
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def enhance(image, algorithm, to_iteration, iteration) do
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infinite_expanse = if is_even(iteration), do: Map.get(algorithm, 511), else: Map.get(algorithm, 0)
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{i_range, j_range} = bounds(image)
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for i <- i_range, j <- j_range, into: %{} do
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{{i, j}, Map.get(algorithm, algorithm_idx(image, {i, j}, infinite_expanse))}
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end
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|> enhance(algorithm, to_iteration, iteration + 1)
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end
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def bounds(image) do
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{{i_min, j_min}, {i_max, j_max}} =
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image
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|> Map.keys()
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|> Enum.min_max()
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{Range.new(i_min - 2, i_max + 2), Range.new(j_min - 2, j_max + 2)}
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end
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def algorithm_idx(image, {i, j}, infinite_expanse) do
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[
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{i - 1, j - 1},
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{i - 1, j},
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{i - 1, j + 1},
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{i, j - 1},
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{i, j},
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{i, j + 1},
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{i + 1, j - 1},
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{i + 1, j},
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{i + 1, j + 1}
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]
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|> Enum.map(&Map.get(image, &1, infinite_expanse))
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|> Enum.map(fn
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true -> 1
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false -> 0
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end)
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|> Integer.undigits(2)
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end
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def input() do
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[unparsed_algorithm, unparsed_source_image] =
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input_string()
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|> String.split("\n\n", trim: true)
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algorithm =
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unparsed_algorithm
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|> String.split("", trim: true)
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|> Enum.with_index()
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|> Enum.map(fn
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{"#", i} -> {i, true}
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{".", i} -> {i, false}
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end)
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|> Enum.into(%{})
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source_image =
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unparsed_source_image
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|> String.split("\n", trim: true)
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|> Enum.map(fn line ->
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line
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|> String.split("", trim: true)
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|> Enum.map(fn
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"#" -> true
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"." -> false
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end)
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|> Enum.with_index()
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end)
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|> Enum.with_index()
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|> then(&for(
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{row, i} <- &1,
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{cell, j} <- row,
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into: %{},
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do: {{i, j}, cell}
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))
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{algorithm, source_image}
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end
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end
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