Day 5: Print Queue

Mix.install([:kino])

Section

input = Kino.Input.textarea("input")

input = Kino.Input.read(input)

Part 1

[ordering, updates] = String.split(input, "\n\n") |> Enum.map(&(String.split(&1, "\n")))
parsed_ordering = Enum.reduce(ordering, %{}, fn (item, acc) -> 
  String.split(item, "|") 
  |> Enum.map(&(String.to_integer(&1)))
  |> then(fn([left, right]) -> 
    {_, acc} = Map.get_and_update(acc, left, fn 
      nil -> {nil, %{after: [right], before: []}}
      list = %{after: list_after, before: list_before} when is_list(list_after) and is_list(list_before) -> {list, %{after: [right | list_after], before: list_before}}
    end)
    {_, acc} = Map.get_and_update(acc, right, fn 
      nil -> {nil, %{after: [], before: [left]}}
      list = %{after: list_after, before: list_before} when is_list(list_after) and is_list(list_before) -> {list, %{before: [left | list_before], after: list_after}}
    end)
    acc
  end)
end)
Enum.map(updates, fn item -> 
  String.split(item, ",") |> Enum.map(&(String.to_integer(&1)))
end)
|> Enum.reduce([], fn(update_line, acc) -> 
  {_, valid_updates} = Enum.reduce(update_line, {0, 0}, fn(num, {curr_num, valid_updates}) ->  
    valid_before = Enum.slice(update_line, 0..(if(curr_num == 0, do: length(update_line)*-1, else: curr_num) - 1)//1)
    |> Enum.all?(fn(i) -> i in parsed_ordering[num][:before] end)
    valid_after = Enum.slice(update_line, (curr_num + 1)..-1//1)
    |> Enum.all?(fn(i) -> i in parsed_ordering[num][:after] end)
    {curr_num + 1, valid_updates + (if(valid_before && valid_after, do: 1, else: 0))}
  end)
  [if(valid_updates == length(update_line), do: Enum.at(update_line, Float.floor(length(update_line)/2) |> trunc()), else: 0) | acc]
end)
|> Enum.sum()

Part 2

[ordering, updates] = String.split(input, "\n\n") |> Enum.map(&(String.split(&1, "\n")))
parsed_ordering = Enum.reduce(ordering, %{}, fn (item, acc) -> 
  String.split(item, "|") 
  |> Enum.map(&(String.to_integer(&1)))
  |> then(fn([left, right]) -> 
    {_, acc} = Map.get_and_update(acc, left, fn 
      nil -> {nil, %{after: [right], before: []}}
      list = %{after: list_after, before: list_before} when is_list(list_after) and is_list(list_before) -> {list, %{after: [right | list_after], before: list_before}}
    end)
    {_, acc} = Map.get_and_update(acc, right, fn 
      nil -> {nil, %{after: [], before: [left]}}
      list = %{after: list_after, before: list_before} when is_list(list_after) and is_list(list_before) -> {list, %{before: [left | list_before], after: list_after}}
    end)
    acc
  end)
end)

into_list = fn(elem, list) ->
  [elem | list]
end

Enum.map(updates, fn item -> 
  String.split(item, ",") |> Enum.map(&(String.to_integer(&1)))
end)
|> Enum.reduce([], fn(update_line, acc) -> 
  {_, valid_updates} = Enum.reduce(update_line, {0, 0}, fn(num, {curr_num, valid_updates}) -> 
    valid_before = Enum.slice(update_line, 0..(if(curr_num == 0, do: length(update_line)*-1, else: curr_num) - 1)//1)
    |> Enum.all?(fn(i) -> i in parsed_ordering[num][:before] end)
    valid_after = Enum.slice(update_line, (curr_num + 1)..-1//1)
    |> Enum.all?(fn(i) -> i in parsed_ordering[num][:after] end)
    {curr_num + 1, valid_updates + (if(valid_before && valid_after, do: 1, else: 0))}
  end)
    if valid_updates != length(update_line) do
      Enum.sort(update_line, fn(left, right) -> left in parsed_ordering[right][:before] end)
      |> Enum.at(Float.floor(length(update_line)/2) |> trunc())
      |> into_list.(acc)
    else
      [0 | acc]
    end
end)
|> Enum.sum()