42 lines
1005 B
Elixir
42 lines
1005 B
Elixir
defmodule Day5 do
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def upcase?(char), do: char in ?A..?Z
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def same_letter?(c1, c2), do: String.upcase(<<c1::utf8>>) === String.upcase(<<c2::utf8>>)
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def case_differs?(c1, c2), do: upcase?(c1) !== upcase?(c2)
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def react?(c1, c2), do: same_letter?(c1, c2) && case_differs?(c1, c2)
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# note: reverses the list - for part 1 doesn't seem to matter
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def react(chars) do
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Enum.reduce(chars, [], fn
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curr, [] -> [curr]
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curr, [prev | old] -> if react?(curr, prev), do: old, else: [curr, prev | old]
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end)
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end
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def part1 do
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File.read!("input")
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|> String.trim()
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|> String.to_charlist()
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|> react()
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|> length()
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end
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def part2 do
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polymer =
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File.read!("input")
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|> String.trim()
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|> String.to_charlist()
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lengths =
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for lower <- ?a..?z, upper = lower - 32 do
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Enum.reject(polymer, &(&1 in [lower, upper]))
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|> react()
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|> length()
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end
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Enum.min(lengths)
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end
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end
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IO.puts(Day5.part1())
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IO.puts(Day5.part2())
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