Day 12

lib/common.ex

@@ -47,4 +47,14 @@ defmodule Aoc2023.Common do
   end
 
   def transpose(l), do: l |> Enum.zip |> Enum.map(&Tuple.to_list/1)
+
+  def collapse(enum, v) do
+    enum
+    |> Stream.zip(enum |> Stream.drop(1) |> Stream.concat([nil]))
+    |> Stream.filter(fn {a, b} -> a != v || b != v end)
+    |> Stream.map(pipe(elem(0)))
+  end
+
+  def repeat(lst, 0), do: []
+  def repeat(lst, n), do: Enum.concat(lst, repeat(lst, n - 1))
 end