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Contents
defmodule Sublist do
@doc """
Returns whether the first list is a sublist or a superlist of the second list
and if not whether it is equal or unequal to the second list.
"""
def compare(a, b) do
case {length(a), length(b)} do
{la, lb} when la < lb ->
if is_sublist(a, b, la, lb), do: :sublist, else: :unequal
{la, lb} when la > lb ->
if is_sublist(b, a, lb, la), do: :superlist, else: :unequal
_ ->
if a == b, do: :equal, else: :unequal
end
end
defp is_sublist(_, _, len_a, len_b) when len_a > len_b, do: false
# empty is sublist of all non-empty
defp is_sublist([], _, _, _), do: true
defp is_sublist(a, b = [_ | t], len_a, len_b) do
if try_is_sublist(a, b) do
true
else
is_sublist(a, t, len_a, len_b - 1)
end
end
defp try_is_sublist([], _), do: true
defp try_is_sublist([x | at], [x | bt]), do: try_is_sublist(at, bt)
defp try_is_sublist(_, _), do: false
end
Version data entries
69 entries across 69 versions & 1 rubygems