2016 Update

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

@@ -1,28 +1,26 @@
 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)
+  def queen(n, display \\ true) do
+    solve(n, [], [], [], display)
   end
 
-  def solve(n, row, _, _) when n <= length(row) do
-    print(n,row)
+  defp solve(n, row, _, _, display) when n==length(row) do
+    if display, do: print(n,row)
     1
   end
-  def solve(n, row, add, sub) do
+  defp solve(n, row, add_list, sub_list, display) 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
+      add = x + length(row)             # \ diagonal check
+      sub = x - length(row)             # / diagonal check
+      if (add in add_list) or (sub in sub_list) do
         0
+      else
+        solve(n, [x|row], [add | add_list], [sub | sub_list], display)
       end
-    end) |> Enum.sum
+    end) |> Enum.sum                    # total of the solution
   end
 
-  def print(n, row) do
-    IO.puts frame = "+-" <> String.duplicate("--", n) <> "+"
+  defp print(n, row) do
+    IO.puts frame = "+" <> String.duplicate("-", 2*n+1) <> "+"
     Enum.each(row, fn x ->
       line = Enum.map_join(0..n-1, fn i -> if x==i, do: "Q ", else: ". " end)
       IO.puts "| #{line}|"
@@ -34,3 +32,7 @@ end
 Enum.each(1..6, fn n ->
   IO.puts " #{n} Queen : #{RC.queen(n)}"
 end)
+
+Enum.each(7..12, fn n ->
+  IO.puts " #{n} Queen : #{RC.queen(n, false)}"             # no display
+end)