aoc2018/day2/day2_2.ex

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Elixir
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2018-12-02 06:04:16 +00:00
input = IO.gets("input?")
|> String.trim
|> String.split(" ")
defmodule Solver do
def to_list(string) do
case string do
"" -> []
_ ->
string
|> String.split("")
|> Enum.filter(fn char ->
char != ""
end)
end
end
# get the common string between the box ids
def get_common(box_id, box_id_2) do
# convert to list
box_id_l = to_list(box_id)
box_id_2_l = to_list(box_id_2)
# zip them
list_chars = Enum.zip(box_id_l, box_id_2_l)
# if theyre equal, we add to the accumulator
common_str = Enum.reduce(list_chars, "", fn tup, acc ->
{c1, c2} = tup
if c1 == c2 do
acc <> c1
else
acc
end
end)
# for common_str to be valid it has to be
# L(common_str) = L(box_id) - 1
# since correct box ids have just *ONE*
# character difference between them
if String.length(common_str) == (String.length(box_id) - 1) do
{:ok, common_str}
else
:not_found
end
end
def solve(input) do
# find all the common strings
# and filter shit
commons = Enum.map(input, fn box_id ->
Enum.map(input, fn box_id_2 ->
common = get_common(box_id, box_id_2)
case common do
:not_found -> nil
{:ok, str} -> str
end
end)
|> Enum.filter(fn combo ->
combo != nil
end)
end)
|> Enum.filter(fn combo ->
combo != []
end)
end
end
res = Solver.solve(input)
IO.puts "result: #{inspect res}"