25 lines
579 B
Plaintext
25 lines
579 B
Plaintext
defmodule Perfect do
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def shuffle(n) do
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start = Enum.to_list(1..n)
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m = div(n, 2)
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shuffle(start, magic_shuffle(start, m), m, 1)
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end
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defp shuffle(start, start, _, step), do: step
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defp shuffle(start, deck, m, step) do
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shuffle(start, magic_shuffle(deck, m), m, step+1)
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end
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defp magic_shuffle(deck, len) do
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{left, right} = Enum.split(deck, len)
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Enum.zip(left, right)
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|> Enum.map(&Tuple.to_list/1)
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|> List.flatten
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end
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end
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Enum.each([8, 24, 52, 100, 1020, 1024, 10000], fn n ->
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step = Perfect.shuffle(n)
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IO.puts "#{n} : #{step}"
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end)
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