2016 Update

Task/Longest-increasing-subsequence/Elixir/longest-increasing-subsequence-1.elixir

@@ -0,0 +1,19 @@
+defmodule Longest_increasing_subsequence do
+  # Naive implementation
+  def lis(l) do
+    (for ss <- combos(l), ss == Enum.sort(ss), do: ss)
+    |> Enum.max_by(fn ss -> length(ss) end)
+  end
+
+  defp combos(l) do
+    Enum.reduce(1..length(l), [[]], fn k, acc -> acc ++ (combos(k, l)) end)
+  end
+  defp combos(1, l), do: (for x <- l, do: [x])
+  defp combos(k, l) when k == length(l), do: [l]
+  defp combos(k, [h|t]) do
+    (for subcombos <- combos(k-1, t), do: [h | subcombos]) ++ combos(k, t)
+  end
+end
+
+IO.inspect Longest_increasing_subsequence.lis([3,2,6,4,5,1])
+IO.inspect Longest_increasing_subsequence.lis([0,8,4,12,2,10,6,14,1,9,5,13,3,11,7,15])

Task/Longest-increasing-subsequence/Elixir/longest-increasing-subsequence-2.elixir

@@ -0,0 +1,28 @@
+defmodule Longest_increasing_subsequence do
+  # Patience sort implementation
+  def patience_lis(l), do: patience_lis(l, [])
+
+  defp patience_lis([h | t], []), do: patience_lis(t, [[{h,[]}]])
+  defp patience_lis([h | t], stacks), do: patience_lis(t, place_in_stack(h, stacks, []))
+  defp patience_lis([], []), do: []
+  defp patience_lis([], stacks), do: get_previous(stacks) |> recover_lis |> Enum.reverse
+
+  defp place_in_stack(e, [stack = [{h,_} | _] | tstacks], prevstacks) when h > e do
+    prevstacks ++ [[{e, get_previous(prevstacks)} | stack] | tstacks]
+  end
+  defp place_in_stack(e, [stack | tstacks], prevstacks) do
+    place_in_stack(e, tstacks, prevstacks ++ [stack])
+  end
+  defp place_in_stack(e, [], prevstacks) do
+    prevstacks ++ [[{e, get_previous(prevstacks)}]]
+  end
+
+  defp get_previous(stack = [_|_]), do: hd(List.last(stack))
+  defp get_previous([]), do: []
+
+  defp recover_lis({e, prev}), do: [e | recover_lis(prev)]
+  defp recover_lis([]), do: []
+end
+
+IO.inspect Longest_increasing_subsequence.patience_lis([3,2,6,4,5,1])
+IO.inspect Longest_increasing_subsequence.patience_lis([0,8,4,12,2,10,6,14,1,9,5,13,3,11,7,15])