Add Elixir BFS and DFS

Author: adlawson

elixir/bfs.ex

@@ -0,0 +1,45 @@
+defmodule Bfs do
+    @moduledoc """
+    Breadth First Search
+    """
+
+    @type t :: Keyword.t
+    @type n :: non_neg_integer
+
+    @doc """
+    Visit all nodes in breadth first order and return a list of the nodes in the
+    order they were visited.
+
+    ## Examples
+
+        iex> Bfs.visit(1, [{1,[2,3]}, {2,[1]}, {3,[1]}])
+        [1,2,3]
+
+    """
+    @spec visit(n, t) :: t
+    def visit(start, nodes) do
+        visit(start, nodes, [])
+    end
+
+    defp visit(node, nodes, visited) do
+        visit_frontier([node], nodes, visited)
+    end
+
+    defp visit_frontier([]=_, _, visited) do
+        visited
+    end
+
+    defp visit_frontier([_|_]=frontier, nodes, visited) do
+        v = visited ++ frontier
+        x = Enum.filter(frontier_adj(frontier, nodes), fn(n) ->
+            !Enum.member?(visited, n)
+        end)
+        visit_frontier(x, nodes, v)
+    end
+
+    defp frontier_adj(frontier, nodes) do
+        Enum.reduce(frontier, [], fn(n, acc) ->
+            acc ++ nodes[n]
+        end)
+    end
+end

elixir/bfs_test.exs

@@ -0,0 +1,15 @@
+# To run: `elixirc bfs.ex && elixir bfs_test.exs`
+IO.inspect(Bfs.visit(1, [
+     {1,  [2, 3, 4]},
+     {2,  [1, 5, 6]},
+     {3,  [1]},
+     {4,  [1, 7, 8]},
+     {5,  [2, 9, 10]},
+     {6,  [2]},
+     {7,  [4, 11, 12]},
+     {8,  [4]},
+     {9,  [5]},
+     {10, [5]},
+     {11, [7]},
+     {12, [7]}
+]))

elixir/dfs.ex

@@ -0,0 +1,36 @@
+defmodule Dfs do
+    @moduledoc """
+    Depth First Search
+    """
+
+    @type t :: Keyword.t
+    @type n :: non_neg_integer
+
+    @doc """
+    Visit all nodes in depth first order and return a list of the nodes in the
+    order they were visited.
+
+    ## Examples
+
+        iex> Dfs.visit(1, [{1,[2,3]}, {2,[1]}, {3,[1]}])
+        [1,2,3]
+
+    """
+    @spec visit(n, t) :: t
+    def visit(start, nodes) do
+        visit(start, nodes, [])
+    end
+
+    defp visit(node, nodes, visited) do
+        Enum.reduce(nodes[node], visited ++ [node], fn(n, acc) ->
+            visit_recur(n, nodes, acc)
+        end)
+    end
+
+    defp visit_recur(node, nodes, visited) do
+        case Enum.member?(visited, node) do
+            true  -> visited
+            false -> visit(node, nodes, visited)
+        end
+    end
+end

elixir/dfs_test.exs

@@ -0,0 +1,15 @@
+# To run: `elixirc dfs.ex && elixir dfs_test.exs`
+IO.inspect(Dfs.visit(1, [
+    {1,  [2, 7, 8]},
+    {2,  [1, 3, 6]},
+    {3,  [2, 4, 5]},
+    {4,  [3]},
+    {5,  [3]},
+    {6,  [2]},
+    {7,  [1]},
+    {8,  [1, 9, 12]},
+    {9,  [8, 10, 11]},
+    {10, [9]},
+    {11, [9]},
+    {12, [8]}
+]))