2016 Update

Task/Spiral-matrix/Elixir/spiral-matrix-1.elixir

@@ -0,0 +1,19 @@
+defmodule RC do
+  def spiral_matrix(n) do
+    wide = length(to_char_list(n*n-1))
+    fmt = String.duplicate("~#{wide}w ", n) <> "~n"
+    runs = Enum.flat_map(n..1, &[&1,&1]) |> tl
+    delta = Stream.cycle([{0,1},{1,0},{0,-1},{-1,0}])
+    running(Enum.zip(runs,delta),0,-1,[])
+    |> Enum.with_index |> Enum.sort |>  Enum.chunk(n)
+    |> Enum.each(fn row -> :io.format fmt, (for {_,i} <- row, do: i) end)
+  end
+
+  defp running([{run,{dx,dy}}|rest], x, y, track) do
+    new_track = Enum.reduce(1..run, track, fn i,acc -> [{x+i*dx, y+i*dy} | acc] end)
+    running(rest, x+run*dx, y+run*dy, new_track)
+  end
+  defp running([],_,_,track), do: track |> Enum.reverse
+end
+
+RC.spiral_matrix(5)

Task/Spiral-matrix/Elixir/spiral-matrix-2.elixir

@@ -0,0 +1,30 @@
+defmodule RC do
+  def spiral_matrix(n) do
+    wide = String.length(to_string(n*n-1))
+    fmt = String.duplicate("~#{wide}w ", n) <> "~n"
+    right(n,n-1,0,[]) |> Enum.reverse |> Enum.with_index |> Enum.sort |> Enum.chunk(n) |>
+      Enum.each(fn row ->
+        :io.format fmt, (for {_,i} <- row, do: i)
+      end)
+  end
+
+  def right(n, side, i, coordinates) do
+    down(n, side, i, Enum.reduce(0..side, coordinates, fn j,acc -> [{i, i+j} | acc] end))
+  end
+
+  def down(_, 0, _, coordinates), do: coordinates
+  def down(n, side, i, coordinates) do
+    left(n, side-1, i, Enum.reduce(1..side, coordinates, fn j,acc -> [{i+j, n-1-i} | acc] end))
+  end
+
+  def left(n, side, i, coordinates) do
+    up(n, side, i, Enum.reduce(side..0, coordinates, fn j,acc -> [{n-1-i, i+j} | acc] end))
+  end
+
+  def up(_, 0, _, coordinates), do: coordinates
+  def up(n, side, i, coordinates) do
+    right(n, side-1, i+1, Enum.reduce(side..1, coordinates, fn j,acc -> [{i+j, i} | acc] end))
+  end
+end
+
+RC.spiral_matrix(5)

Task/Spiral-matrix/Elixir/spiral-matrix-3.elixir

@@ -0,0 +1,19 @@
+defmodule RC do
+  def spiral_matrix(n) do
+    fmt = String.duplicate("~#{length(to_char_list(n*n-1))}w ", n) <> "~n"
+    Enum.flat_map(n..1, &[&1, &1])
+    |> tl
+    |> Enum.reduce({{0,-1},{0,1},[]}, fn run,{{x,y},{dx,dy},acc} ->
+         side = for i <- 1..run, do: {x+i*dx, y+i*dy}
+         {{x+run*dx, y+run*dy}, {dy, -dx}, acc++side}
+       end)
+    |> elem(2)
+    |> Enum.with_index
+    |> Enum.sort
+    |> Enum.map(fn {_,i} -> i end)
+    |> Enum.chunk(n)
+    |> Enum.each(fn row -> :io.format fmt, row end)
+  end
+end
+
+RC.spiral_matrix(5)

Task/Spiral-matrix/Elixir/spiral-matrix.elixir

@@ -1,33 +0,0 @@
-defmodule RC do
-  def spiral_matrix(n) do
-    right(n,n-1,0,[]) |> Enum.with_index |> Enum.sort |>  Enum.with_index |>
-      Enum.each(fn {{_,x},i} ->
-        :io.format("~2w ", [x])
-        if( rem(i+1,n)==0, do: IO.puts "")
-      end)
-  end
-
-  def right(n,side,i,coordinates) do
-    coord = for j <- 0..side, do: {i, i+j}
-    down(n,side,i,coordinates++coord)
-  end
-
-  def down(_,0,_,coordinates), do: coordinates
-  def down(n,side,i,coordinates) do
-    coord = for j <- 1..side, do: {i+j, n-1-i}
-    left(n,side-1,i,coordinates++coord)
-  end
-
-  def left(n,side,i,coordinates) do
-    coord = for j <- 0..side, do: {n-1-i, i+side-j}
-    up(n,side,i,coordinates++coord)
-  end
-
-  def up(_,0,_,coordinates), do: coordinates
-  def up(n,side,i,coordinates) do
-    coord = for j <- 1..side, do: {i+side-j+1, i}
-    right(n,side-1,i+1,coordinates++coord)
-  end
-end
-
-RC.spiral_matrix(5)