76 lines
1.5 KiB
Elixir
76 lines
1.5 KiB
Elixir
defmodule Day2 do
|
|
def count_characters(id) do
|
|
id
|
|
|> String.graphemes()
|
|
|> Enum.reduce(%{}, fn c, acc ->
|
|
Map.update(acc, c, 1, &(&1 + 1))
|
|
end)
|
|
end
|
|
|
|
def checksum(list) do
|
|
characters = Enum.map(list, &count_characters/1)
|
|
two = Enum.count(characters, any_char_count(2))
|
|
three = Enum.count(characters, any_char_count(3))
|
|
two * three
|
|
end
|
|
|
|
defp any_char_count(n) do
|
|
fn map ->
|
|
map
|
|
|> Enum.to_list()
|
|
|> Enum.any?(fn {_c, count} -> count == n end)
|
|
end
|
|
end
|
|
|
|
def diff(a, b) do
|
|
a = String.graphemes(a)
|
|
b = String.graphemes(b)
|
|
Enum.zip(a, b)
|
|
|> Enum.reduce({0, ""}, fn {a, b}, {diff_count, common} ->
|
|
cond do
|
|
a == b ->
|
|
{diff_count, common <> a}
|
|
true ->
|
|
{diff_count + 1, common}
|
|
end
|
|
end)
|
|
end
|
|
|
|
def match(id, list) do
|
|
Enum.reduce_while(list, nil, fn other_id, _acc ->
|
|
case diff(id, other_id) do
|
|
{1, common} -> {:halt, common}
|
|
_ -> {:cont, nil}
|
|
end
|
|
end)
|
|
end
|
|
|
|
def correct_boxes(list) do
|
|
list
|
|
|> Enum.reduce_while(nil, fn id, _acc ->
|
|
case match(id, list) do
|
|
nil -> {:cont, nil}
|
|
common -> {:halt, common}
|
|
end
|
|
end)
|
|
end
|
|
|
|
def except(list, except) do
|
|
Enum.reject(list, fn el -> el == except end)
|
|
end
|
|
|
|
defp parse_input() do
|
|
File.read!("lib/day2/input.txt")
|
|
|> String.split("\n")
|
|
end
|
|
|
|
def part1() do
|
|
parse_input()
|
|
|> checksum()
|
|
end
|
|
|
|
def part2() do
|
|
parse_input()
|
|
|> correct_boxes()
|
|
end
|
|
end |