[Sync Iteration] elixir/run-length-encoding/2

solutions/elixir/run-length-encoding/2/lib/run_length_encoder.ex

@@ -0,0 +1,24 @@
+defmodule RunLengthEncoder do
+  @doc """
+  Generates a string where consecutive elements are represented as a data value and count.
+  "AABBBCCCC" => "2A3B4C"
+  For this example, assume all input are strings, that are all uppercase letters.
+  It should also be able to reconstruct the data into its original form.
+  "2A3B4C" => "AABBBCCCC"
+  """
+  @spec encode(String.t()) :: String.t()
+  def encode(string) do
+    Regex.replace(~r/(.)\1*/, string, fn
+      letter, letter -> letter
+      match, letter -> "#{byte_size(match)}" <> letter
+    end)
+  end
+
+  @spec decode(String.t()) :: String.t()
+  def decode(string) do
+    Regex.replace(~r/([0-9]*)(.)/, string, fn
+      _, "", letter -> letter
+      _, count, letter -> String.duplicate(letter, String.to_integer(count))
+    end)
+  end
+end