22 lines
708 B
Plaintext
22 lines
708 B
Plaintext
defmodule Smith do
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def number?(n) do
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d = decomposition(n)
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length(d)>1 and sum_digits(n) == Enum.map(d, &sum_digits/1) |> Enum.sum
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end
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defp sum_digits(n) do
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Integer.digits(n) |> Enum.sum
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end
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defp decomposition(n, k\\2, acc\\[])
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defp decomposition(n, k, acc) when n < k*k, do: [n | acc]
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defp decomposition(n, k, acc) when rem(n, k) == 0, do: decomposition(div(n, k), k, [k | acc])
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defp decomposition(n, k, acc), do: decomposition(n, k+1, acc)
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end
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m = 10000
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smith = Enum.filter(1..m, &Smith.number?/1)
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IO.puts "#{length(smith)} smith numbers below #{m}:"
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IO.puts "First 10: #{Enum.take(smith,10) |> Enum.join(", ")}"
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IO.puts "Last 10: #{Enum.take(smith,-10) |> Enum.join(", ")}"
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