Another update from ingydotnet^djgoku

Task/N-queens-problem/Elixir/n-queens-problem.elixir

@@ -0,0 +1,36 @@
+defmodule RC do
+  def queen(n) do
+    add = Tuple.duplicate(true, 2*n-1)
+    sub = Tuple.duplicate(true, 2*n-1)
+    solve(n, [], add, sub)
+  end
+
+  def solve(n, row, _, _) when n <= length(row) do
+    print(n,row)
+    1
+  end
+  def solve(n, row, add, sub) do
+    Enum.map(Enum.to_list(0..n-1) -- row, fn x ->
+      iadd = x + (len = length(row))
+      isub = if (y = x-len) < 0, do: y + 2*n - 1, else: y
+      if elem(add, iadd) and elem(sub, isub) do
+        solve(n, [x|row], put_elem(add,iadd,false), put_elem(sub,isub,false))
+      else
+        0
+      end
+    end) |> Enum.sum
+  end
+
+  def print(n, row) do
+    IO.puts frame = "+-" <> String.duplicate("--", n) <> "+"
+    Enum.each(row, fn x ->
+      line = Enum.map_join(0..n-1, fn i -> if x==i, do: "Q ", else: ". " end)
+      IO.puts "| #{line}|"
+    end)
+    IO.puts frame
+  end
+end
+
+Enum.each(1..6, fn n ->
+  IO.puts " #{n} Queen : #{RC.queen(n)}"
+end)