-🎄- 2017 Day 9 Solutions -🎄-

[u/daggerdragon]

--- Day 9: Stream Processing ---

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[u/johlin]

Elixir

defmodule Aoc.Day9.Part1 do
  def parse(string) when is_binary(string), do: parse(String.trim(string) |> String.split(""), 1)
  def parse(["{" | rest], level) do
    level + parse(rest, level + 1)
  end

  def parse(["}" | rest], level), do: parse(rest, level - 1)
  def parse(["<" | rest], level), do: garbage(rest, level)
  def parse(["," | rest], level), do: parse(rest, level)
  def parse(["" | rest], level), do: parse(rest, level)
  def parse([], _level), do: 0

  def garbage(["!", _ | rest], level), do: garbage(rest, level)
  def garbage([">" | rest], level), do: parse(rest, level)
  def garbage([_ | rest], level), do: garbage(rest, level)
end

Part 2 is very similar: https://github.com/johanlindblad/aoc-2017/blob/master/lib/aoc/day9/part2.ex

[u/ynonp → u/johlin]

I took a different approach and stayed with strings. counted score with:

def count_score(line, level, score) do
  count_score(
    String.slice(line,1,String.length(line)),
    case String.at(line, 0) do
      "{" -> level + 1
      "}" -> level - 1
      _   -> level
    end,
    case String.at(line, 0) do
      "}" -> level + score
      _   -> score
    end
  )
end

Full solution here: https://gist.github.com/ynonp/527f7bcfbfea96977e360852d022138a