56 lines
1.4 KiB
Elixir
56 lines
1.4 KiB
Elixir
defmodule AOC.Day13 do
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use AOC.Day, day: 13
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def parse_input(lines) do
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lines
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|> Enum.chunk_by(&(&1 == ""))
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|> Enum.reject(&(&1 == [""]))
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|> Enum.map(fn pattern ->
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Enum.map(pattern, &String.to_charlist/1)
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end)
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end
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def find_horizontal_reflection(pattern, required_differences) do
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Enum.find(1..(length(pattern) - 1), fn cut_size ->
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{upper_pattern, lower_pattern} = Enum.split(pattern, cut_size)
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upper_pattern =
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upper_pattern
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|> Enum.reverse()
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|> List.flatten()
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lower_pattern = List.flatten(lower_pattern)
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differences =
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Enum.zip(upper_pattern, lower_pattern)
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|> Enum.count(fn {symbol1, symbol2} -> symbol1 != symbol2 end)
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differences == required_differences
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end)
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end
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def find_vertical_reflection(pattern, required_differences) do
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pattern
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|> List.zip()
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|> Enum.map(&Tuple.to_list/1)
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|> find_horizontal_reflection(required_differences)
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end
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def calculate_summary(patterns, required_differences) do
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Enum.map(patterns, fn pattern ->
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case find_horizontal_reflection(pattern, required_differences) do
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nil -> find_vertical_reflection(pattern, required_differences)
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x -> 100 * x
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end
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end)
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|> Enum.sum()
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end
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def part1(input) do
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calculate_summary(input, 0)
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end
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def part2(input) do
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calculate_summary(input, 1)
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end
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end
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