23 lines
804 B
Elixir
23 lines
804 B
Elixir
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defmodule Sublist do
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@type result ::
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:sublist
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| :superlist
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| :unequal
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| :equal
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@doc """
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Returns whether the first list is a sublist or a superlist of the second list
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and if not whether it is equal or unequal to the second list.
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"""
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def compare(a, a), do: :equal
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def compare(a, b) when length(a) > length(b), do: (if subset?(b, a), do: :superlist, else: :unequal)
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def compare(a, b) when length(a) < length(b), do: (if subset?(a, b), do: :sublist, else: :unequal)
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def compare(_, _), do: :unequal
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defp subset?(a, b, index \\ 0)
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defp subset?([], _b, _index), do: true
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defp subset?(a, b, index) when index + length(a) > length(b), do: false
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defp subset?(a, b, index), do:
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(if Enum.slice(b, index, length(a)) === a, do: true, else: subset?(a, b, index + 1))
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end
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