nucleotide count + robot simulator solutions elixir

elixir/nucleotide-count/lib/nucleotide_count.ex

@@ -0,0 +1,32 @@
+defmodule NucleotideCount do
+  @doc """
+  Counts individual nucleotides in a DNA strand.
+
+  ## Examples
+
+  iex> NucleotideCount.count('AATAA', ?A)
+  4
+
+  iex> NucleotideCount.count('AATAA', ?T)
+  1
+  """
+  @spec count(charlist(), char()) :: non_neg_integer()
+  def count(strand, nucleotide) do
+    Enum.count(strand, &(&1 == nucleotide))
+  end
+
+  @doc """
+  Returns a summary of counts by nucleotide.
+
+  ## Examples
+
+  iex> NucleotideCount.histogram('AATAA')
+  %{?A => 4, ?T => 1, ?C => 0, ?G => 0}
+  """
+  @spec histogram(charlist()) :: map()
+  def histogram(strand) do
+    Enum.reduce(strand, %{?A => 0, ?T => 0, ?C => 0, ?G => 0}, fn nucleotide, counts ->
+      Map.update(counts, nucleotide, 1, &(&1 + 1))
+    end)
+  end
+end