heck around in elixir

02/02.exs

@@ -0,0 +1,38 @@
+regex = ~r{\A(\d+)-(\d+) (\w): (\w+)\z}
+
+list = File.read!("input.txt")
+|> String.split("\n")
+|> Enum.map(&Regex.run(regex, &1, capture: :all_but_first)) # "all but first" removes matching substring, leaving only capture groups
+|> Enum.map(
+	fn [n1, n2, character, password] ->
+		{
+			String.to_integer(n1),
+			String.to_integer(n2),
+			character,
+			String.graphemes(password) # into array of letters
+		}
+	end
+)
+
+IO.puts "Part 1: "
+list
+|> Enum.filter(
+	fn {minimum, maximum, character, password} ->
+		count = Enum.count(password, &(&1 == character))
+		minimum <= count and count <= maximum
+	end
+)
+|> Enum.count()
+|> IO.puts()
+
+IO.puts "Part 2: "
+list
+|> Enum.filter(
+	fn {p1, p2, character, password} ->
+		first = Enum.at(password, p1-1) == character
+		second = Enum.at(password, p2-1) == character
+		(first and !second) or (!first and second)
+	end
+)
+|> Enum.count()
+|> IO.puts()