1 files changed, 45 insertions, 0 deletions
diff --git a/challenge-251/wambash/elixir/ch-1.exs b/challenge-251/wambash/elixir/ch-1.exs
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+defmodule Concatenation do
+  def iter([]) do
+    nil
+  end
+
+  def iter([o]) do
+    {o, []}
+  end
+
+  def iter([f | t]) do
+    with [l | t] <- Enum.reverse(t) do
+      {String.to_integer("#{f}#{l}"), Enum.reverse(t)}
+    end
+  end
+
+  def value(ints) do
+    ints
+    |> Stream.unfold(&iter/1)
+    |> Enum.sum()
+  end
+end
+
+ExUnit.start()
+
+defmodule ConcatenationTest do
+  use ExUnit.Case
+
+  test "concatenation value" do
+    assert Concatenation.iter([6, 12, 25, 1]) == {61, [12, 25]}
+    assert Concatenation.iter([12, 25]) == {1225, []}
+    assert Concatenation.iter([]) == nil
+    assert Concatenation.value([6, 12, 25, 1]) == 1286
+  end
+
+  test "concatenation value more elems" do
+    assert Concatenation.iter([10, 7, 31, 5, 2, 2]) == {102, [7, 31, 5, 2]}
+    assert Concatenation.value([10, 7, 31, 5, 2, 2]) == 489
+  end
+
+  test "concatenation value odd elems" do
+    assert Concatenation.iter([1, 2, 10]) == {110, [2]}
+    assert Concatenation.iter([2]) == {2, []}
+    assert Concatenation.value([1, 2, 10]) == 112
+  end
+end