31 lines
1001 B
Plaintext
31 lines
1001 B
Plaintext
defmodule RC do
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def range_extract(list) do
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max = Enum.max(list) + 2
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sorted = Enum.sort([max|list])
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candidate_number = hd(sorted)
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current_number = hd(sorted)
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extract(tl(sorted), candidate_number, current_number, [])
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end
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defp extract([], _, _, range), do: Enum.reverse(range) |> Enum.join(",")
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defp extract([next|rest], candidate, current, range) when current+1 >= next do
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extract(rest, candidate, next, range)
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end
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defp extract([next|rest], candidate, current, range) when candidate == current do
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extract(rest, next, next, [to_string(current)|range])
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end
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defp extract([next|rest], candidate, current, range) do
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separator = if candidate+1 == current, do: ",", else: "-"
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str = "#{candidate}#{separator}#{current}"
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extract(rest, next, next, [str|range])
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end
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end
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list = [
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0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
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15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
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25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
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37, 38, 39
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]
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IO.inspect RC.range_extract(list)
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