advent-of-code/2018/elixir/lib/two.ex

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Elixir
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2019-12-01 14:55:48 -06:00
defmodule Two do
def bool_int(true), do: 1
def bool_int(false), do: 0
def part1(id_list) do
id_list
|> Stream.map(fn id ->
id
|> String.codepoints()
|> Enum.reduce(%{}, fn l, acc -> Map.update(acc, l, 1, &(&1 + 1)) end)
|> Map.values()
|> MapSet.new()
end)
|> Enum.to_list()
|> Enum.reduce([0, 0], fn s, [x, y] ->
[x + bool_int(2 in s), y + bool_int(3 in s)]
end)
|> Enum.reduce(1, fn i, a -> a * i end)
end
def part2(id_list) do
id_list
|> Stream.map(&String.trim_trailing/1)
|> Enum.to_list()
|> permute_all_pairs()
|> List.flatten()
|> Enum.reduce_while("", fn {id1, id2}, _ ->
case String.myers_difference(id1, id2) do
[eq: p1, del: <<_x::size(8)>>, ins: <<_y::size(8)>>, eq: p2] -> {:halt, p1 <> p2}
_ -> {:cont, ""}
end
end)
end
def permute_all_pairs([]), do: []
def permute_all_pairs(list), do: [permute_pairs(list) | permute_all_pairs(tl(list))]
def permute_pairs([]), do: []
def permute_pairs([cur | rest]), do: Enum.map(rest, &{cur, &1})
end