AdventOfCode/2022/day3.exs

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Elixir
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2022-12-03 05:36:40 +00:00
defmodule Day3 do
def part1(input) do
input
|> Enum.map(fn str ->
size = byte_size(str)
str
|> String.split("", trim: true)
|> Enum.split(div(size, 2))
end)
|> Enum.map(fn {a, b} -> hd(a -- a -- b) end)
|> Enum.map(&score/1)
|> Enum.sum()
end
defp score(<<lower::utf8>>) when lower in ?a..?z, do: lower - ?a + 1
defp score(<<upper::utf8>>) when upper in ?A..?Z, do: upper - ?A + 27
def part2(input) do
input
|> Enum.map(&String.split(&1, "", trim: true))
|> Enum.chunk_every(3)
|> Enum.map(fn [a, b, c] ->
d = a -- a -- b
hd(d -- d -- c)
end)
|> Enum.map(&score/1)
|> Enum.sum()
end
def input do
with [input_filename] <- System.argv(),
{:ok, input} <- File.read(input_filename) do
String.split(input, "\n", trim: true)
else
_ -> :error
end
end
#######################
# HERE BE BOILERPLATE #
#######################
def run do
case input() do
:error -> print_usage()
input -> run_parts_with_timer(input)
end
end
defp run_parts_with_timer(input) do
run_with_timer(1, fn -> part1(input) end)
run_with_timer(2, fn -> part2(input) end)
end
defp run_with_timer(part, fun) do
{time, result} = :timer.tc(fun)
IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
IO.puts("#{result}\n")
end
defp format_time(μsec) when μsec < 1_000, do: "#{μsec}μs"
defp format_time(μsec) when μsec < 1_000_000, do: "#{μsec / 1000}ms"
defp format_time(μsec), do: "#{μsec / 1_000_000}s"
defp print_usage do
IO.puts("Usage: elixir day3.exs input_filename")
end
end
Day3.run()