Add Elixir example for breadth-first search

06_breadth-first_search/elixir/01_breadth-first_search.exs

@@ -0,0 +1,52 @@
+defmodule BreadthFirstSearch do
+  def search(graph, initial_vertex, search_fn) do
+    initial_search_queue = list_to_queue(graph[initial_vertex])
+    do_search(initial_search_queue, search_fn, [], graph)
+  end
+
+  defp do_search(_empty_queue = {[], []}, _, _, _), do: nil
+
+  defp do_search(search_queue, search_fn, searched_list, graph) do
+    {{:value, value}, rest_queue} = :queue.out(search_queue)
+
+    cond do
+      value in searched_list ->
+        do_search(rest_queue, search_fn, searched_list, graph)
+
+      search_fn.(value) ->
+        value
+
+      true ->
+        continue_search(rest_queue, value, search_fn, searched_list, graph)
+    end
+  end
+
+  defp continue_search(search_queue, value, search_fn, searched_list, graph) do
+    join_with_search_queue = &:queue.join(search_queue, &1)
+
+    updated_search_queue =
+      graph[value]
+      |> list_to_queue()
+      |> join_with_search_queue.()
+
+    do_search(updated_search_queue, search_fn, [value | searched_list], graph)
+  end
+
+  defp list_to_queue(list), do: :queue.from_list(list)
+end
+
+graph = %{
+  "you" => ["alice", "bob", "claire"],
+  "bob" => ["anuj", "peggy"],
+  "alice" => ["peggy"],
+  "claire" => ["thom", "jonny"],
+  "anuj" => [],
+  "peggy" => [],
+  "thom" => [],
+  "jonny" => []
+}
+
+person_is_seller? = &String.ends_with?(&1, "m")
+
+name = BreadthFirstSearch.search(graph, "you", person_is_seller?)
+IO.puts("#{name} is a mango seller!")