Created
November 25, 2024 15:50
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defmodule SecretSanta do | |
@participants [:andrei, :dave, :john, :mary, :jane, :anna] | |
def get_random, do: generate_pairs() |> Enum.random() | |
defp generate_pairs(givers \\ @participants, receivers \\ @participants, existing_pairs \\ []) | |
defp generate_pairs([giver | givers], receivers, existing_pairs) do | |
for receiver <- receivers, | |
valid_pair?(giver, receiver, existing_pairs), | |
remaining_receivers = List.delete(receivers, receiver), | |
pairs <- generate_pairs(givers, remaining_receivers, [{giver, receiver} | existing_pairs]) do | |
[{giver, receiver} | pairs] | |
end | |
end | |
defp generate_pairs([], [], _existing_pairs), do: [[]] | |
defp valid_pair?(giver, receiver, existing_pairs) do | |
cond do | |
giver == receiver -> false | |
{giver, receiver} == {:andrei, :dave} -> false | |
{giver, receiver} == {:dave, :andrei} -> false | |
{giver, receiver} == {:john, :mary} -> false | |
{giver, receiver} == {:mary, :john} -> false | |
Enum.member?(existing_pairs, {receiver, giver}) -> false | |
true -> true | |
end | |
end | |
end |
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