Factors of an integer: Difference between revisions
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(→{{header|Elixir}}: add recursive version) |
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(for i <- 1..div(n,2), rem(n,i)==0, do: i) ++ [n] |
(for i <- 1..div(n,2), rem(n,i)==0, do: i) ++ [n] |
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end |
end |
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# Recursive (faster version); |
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def divisor(n), do: divisor(n, 1, []) |> Enum.sort |
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defp divisor(n, i, factors) when n < i*i , do: factors |
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defp divisor(n, i, factors) when n == i*i , do: [i | factors] |
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defp divisor(n, i, factors) when rem(n,i)==0, do: divisor(n, i+1, [i, div(n,i) | factors]) |
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defp divisor(n, i, factors) , do: divisor(n, i+1, factors) |
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end |
end |
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Enum.each([45, 53, 64], fn n -> |
Enum.each([45, 53, 60, 64], fn n -> |
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IO.puts "#{n}: #{inspect RC.factor(n)}" |
IO.puts "#{n}: #{inspect RC.factor(n)}" |
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end) |
end) |
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IO.puts "\nRange: #{inspect range = 1..10000}" |
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funs = [ factor: &RC.factor/1, |
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divisor: &RC.divisor/1 ] |
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Enum.each(funs, fn {name, fun} -> |
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{time, value} = :timer.tc(fn -> Enum.count(range, &length(fun.(&1))==2) end) |
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IO.puts "#{name}\t prime count : #{value},\t#{time/1000000} sec" |
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end) |
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</lang> |
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{{out}} |
{{out}} |
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45: [1, 3, 5, 9, 15, 45] |
45: [1, 3, 5, 9, 15, 45] |
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53: [1, 53] |
53: [1, 53] |
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60: [1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60] |
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64: [1, 2, 4, 8, 16, 32, 64] |
64: [1, 2, 4, 8, 16, 32, 64] |
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Range: 1..10000 |
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factor prime count : 1229, 7.316 sec |
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divisor prime count : 1229, 0.265 sec |
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</pre> |
</pre> |
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