ee96a818e1
- Clear the boilerplate that `mix` generated - Consume `Math.factor` to test which inputs are semiprimes - Cache all inputs that are semiprimes as soon as we discover that they are - semiprimes I considered a couple things related to the Cache: - Could save space by storing all semiprime factors in a tree. This would make the lookups more expensive. Also because the tree's depth would never exceed two (because all semiprimes only have two factors), the tree would be quite broad, and we may not be saving enough space for the trade to be worthwhile. I might be wrong about that though. - We could consider pre-computing all semiprimes when we start the app, but without running some tests firsts, I'm not sure whether or not it's worth the trouble.
33 lines
547 B
Elixir
33 lines
547 B
Elixir
defmodule Server do
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@moduledoc """
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Documentation for `Server`.
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"""
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@doc """
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If `n` contains exactly two prime factors, return those prime factors;
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otherwise, return nothing.
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"""
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def semiprime(n) do
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case Cache.get(n) do
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nil ->
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case do_semiprime(n) do
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nil ->
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nil
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res ->
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Cache.put(n, res)
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res
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end
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hit ->
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hit
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end
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end
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defp do_semiprime(n) do
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case Math.factor(n) do
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[_, _] = res -> res
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_ -> nil
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end
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end
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end
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