day5.ex

defmodule Advent2018.Day5 do
  def solve(input) do
    parse_polymers(input, <<>>)
  end

  def parse_polymers(<<>>, acc), do: byte_size(acc)
  
  def parse_polymers(<<a, rest :: binary>>, <<b, seen :: binary>>) when abs(a-b) == 32 do
    parse_polymers(rest, seen)
  end
  
  def parse_polymers(<<a, b, rest :: binary>>, seen) when abs(a-b) ==32 do
    parse_polymers(rest, seen)
  end

  def parse_polymers(<<"\n", rest :: binary>>, seen) do
    parse_polymers(rest, seen)
  end

  def parse_polymers(<<a, rest :: binary>>, seen) do
    parse_polymers(rest, <<a>> <> seen)
  end
end