Add Duplicate Character Counter in Elixir

Author: ricardomaps

archive/e/elixir/duplicate-character-counter.ex

@@ -0,0 +1,21 @@
+case System.argv() do
+  [str] when byte_size(str) > 0 ->
+    chars = String.graphemes(str)
+
+    frequencies = Enum.reduce(chars, %{}, fn el, acc ->
+      Map.update(acc, el, 1, &(&1 + 1))
+    end) |> Enum.filter(fn {_, count} -> count > 1 end) |> Map.new()
+
+    if Enum.empty?(frequencies) do
+      IO.puts("No duplicate characters")
+    else
+      chars
+      |> Enum.uniq()
+      |> Enum.each(fn char ->
+        if Map.has_key?(frequencies, char) do
+          IO.puts("#{char}: #{frequencies[char]}")
+        end
+      end)
+    end
+  _ -> IO.puts("Usage: please provide a string")
+end