represent record of searched verices as a hash for O(1) lookup

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

@@ -18,16 +18,16 @@ def search(name)
   search_queue = []
   search_queue += @graph[name]
   # This array is how you keep track of which people you've searched before.
-  searched = []
+  searched = {}
 
   until search_queue.empty?
     person = search_queue.shift
     # Only search this person if you haven't already searched them.
-    next if searched.member?(person)
+    next if searched[person]
     return person if yield person
     search_queue += @graph[person]
       # Marks this person as searched
-    searched.push(person)
+    searched[person] = true
   end
 
   false