33 lines
1.1 KiB
Plaintext
33 lines
1.1 KiB
Plaintext
defmodule Hamming do
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def generater do
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queues = [{2, queue}, {3, queue}, {5, queue}]
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Stream.unfold({1, queues}, fn {n, q} -> next(n, q) end)
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end
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defp next(n, queues) do
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queues = Enum.map(queues, fn {m, queue} -> {m, push(queue, m*n)} end)
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min = Enum.map(queues, fn {_, queue} -> top(queue) end) |> Enum.min
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queues = Enum.map(queues, fn {m, queue} ->
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{m, (if min==top(queue), do: erase_top(queue), else: queue)}
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end)
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{n, {min, queues}}
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end
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defp queue, do: {[], []}
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defp push({input, output}, term), do: {[term | input], output}
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defp top({input, []}), do: List.last(input)
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defp top({_, [h|_]}), do: h
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defp erase_top({input, []}), do: erase_top({[], Enum.reverse(input)})
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defp erase_top({input, [_|t]}), do: {input, t}
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end
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IO.puts "first twenty Hamming numbers:"
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IO.inspect Hamming.generater |> Enum.take(20)
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IO.puts "1691st Hamming number:"
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IO.puts Hamming.generater |> Enum.take(1691) |> List.last
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IO.puts "one millionth Hamming number:"
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IO.puts Hamming.generater |> Enum.take(1_000_000) |> List.last
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