avoid use of global variables; it is more rubyish to represent a graph as a class

06_breadth-first_search/ruby/01_breadth-first_search.rb

@@ -2,35 +2,38 @@ def person_is_seller?(name)
   name[-1] == "m"
 end
 
-@graph = {}
+class Graph < Hash
+  def search(name)
+    search_queue = []
+    search_queue += self[name]
+    # This array is how you keep track of which people you've searched before.
+    searched = {}
 
-# %w(string1 string2 ...) is a shorter way to define arrays of strings
+    until search_queue.empty?
-@graph["you"] = %w(alice bob claire)
+      pp searched
-@graph["bob"] = %w(anuj peggy)
+      person = search_queue.shift
-@graph["alice"] = %w(peggy)
+      # Only search this person if you haven't already searched them.
-@graph["claire"] = %w(thom jonny)
+      next if searched[person]
-@graph["anuj"] = []
+      return person if yield person
-@graph["peggy"] = []
+      search_queue += self[person]
-@graph["thom"] = []
+        # Marks this person as searched
-@graph["jonny"] = []
+      searched[person] = true
+    end
 
-def search(name)
+    false
-  search_queue = []
-  search_queue += @graph[name]
-  # This array is how you keep track of which people you've searched before.
-  searched = {}
-
-  until search_queue.empty?
-    person = search_queue.shift
-    # Only search this person if you haven't already searched them.
-    next if searched[person]
-    return person if yield person
-    search_queue += @graph[person]
-      # Marks this person as searched
-    searched[person] = true
   end
-
-  false
 end
 
-search("you"){|person| person_is_seller?(person) }.tap{|person| puts "#{person} is a mango seller!" if person}
+
+# %w(string1 string2 ...) is a shorter way to define arrays of strings
+graph = Graph.new
+graph["you"] = %w(alice bob claire)
+graph["bob"] = %w(anuj peggy)
+graph["alice"] = %w(peggy)
+graph["claire"] = %w(thom jonny)
+graph["anuj"] = []
+graph["peggy"] = []
+graph["thom"] = []
+graph["jonny"] = []
+
+graph.search("you"){|person| person_is_seller?(person) }.tap{|person| puts "#{person} is a mango seller!" if person}