Commit 50efcb1

@@ -1,22 +1,35 @@
 <<-DOC
-[2:10 PM] Marvin Liu: You are given a single linked list, and you are asked to determine if there is a circle inside it
-[2:11 PM] Marvin Liu: A circle means, a -> b -> c -> b, then it is a circle
+You are given a single linked list, and you are asked to determine if there is a circle inside it
+A circle means, a -> b -> c -> b, then it is a circle
 DOC
+require 'byebug'
 
-def circle?(head)
-  true
+def circle?(list)
+  tortoise, hare = list, list.next_item
+
+  until hare.nil?
+    return true if tortoise == hare
+    tortoise = tortoise.next_item
+    hare = hare.next_item.next_item
+  end
+
+  return false
 end
 
 class Node
   attr_reader :next_item, :value
 
   def initialize(value)
-    @value
+    @value = value
   end
 
   def add(value)
     @next_item = value.is_a?(Node) ? value : Node.new(value)
   end
+
+  def inspect
+    "#{object_id} #{value}"
+  end
 end
 
 a = Node.new("A")