Advent of Code. Day 5.

advent-5.ex

is_nice_string = fn (line) ->
	line = String.strip(line)
	result = line |> String.codepoints |> Enum.reduce {0, 0, 0, ""}, fn char, {vowels, doubles, invalid, last_char} ->
		if last_char == char do
			doubles = doubles + 1
		end

		if char in ["a", "e", "i", "o", "u"] do
			vowels = vowels + 1
		end

		if (last_char <> char) in ["ab", "cd", "pq", "xy"] do
			invalid = invalid + 1
		end

		{vowels, doubles, invalid, char}
	end

	case result do
		{_, _, invalid, _} when invalid > 0 -> {:no, :invalid_chars}
		{_, 0, _, _} -> {:no, :no_repeating_chars}
		{vowels, _, _, _} when vowels < 3 -> {:no, :not_enough_vowels}
		_ -> :yes
	end
end

is_nice_string_2 = fn (line) ->
	line = String.strip(line)
	{pairs, repeating_chars, _, _, _} = line |> String.codepoints |> Enum.reduce {[], 0, "", "", ""}, fn char, {pairs, repeating_chars, last_pair, penultimate_char, last_char} ->
		if char == penultimate_char do
			repeating_chars = repeating_chars + 1
		end

		pair = last_char <> char

		cond do
			last_char != "" and pair != last_pair -> pairs = [ pair | pairs ]
			pair == last_pair -> pair = ""
			true -> :ok
		end

		{pairs, repeating_chars, pair, last_char, char}
	end

	cond do
		repeating_chars < 1 -> {:no, :no_repeating_chars}
		length(Enum.uniq(pairs)) == length(pairs) -> {:no, :no_repeating_pairs}
		true -> :yes
	end
end


input_stream = File.stream!("input.txt")
nice_strings = Enum.reduce(input_stream, 0, fn line, acc ->
	case is_nice_string.(line) do
		:yes -> acc + 1
		_ -> acc
	end
end)
IO.puts nice_strings

nice_strings_2 = Enum.reduce(input_stream, 0, fn line, acc ->
	case is_nice_string_2.(line) do
		:yes -> acc + 1
		_ -> acc
	end
end)
IO.puts nice_strings_2