title: Algorithm for finding internally connected cluster of nodes within a graph from which no edge points outwards
body: <p>I am representing my graph as a adjacency list. I want to know how can I find a cluster of nodes which are internally connected but no edge points outwards from them. Is there any well known algorithm out there which I can use?</p>
  
  <p>for e.g.This is my graph.</p>
  
  <pre><code>1----&gt;2
  2----&gt;1
  2----&gt;3
  3----&gt;1
  3----&gt;4
  4----&gt;5
  5----&gt;4
  </code></pre>
  
  <p>Here nodes 4 and 5 are internally connected. Yet no outside edge comes from this. This would be my answer. Similarly nodes 1,2,3 even though they form a cycle, do not fit the criteria as an outside edge emanates from node 3.
  So it is not same as finding a cycle in a adjacency list.</p>
  
  <p>Optional read: (why I need this)
  I am working on a Ranking page (search engine) algorithm, nodes like 4 and 5 are called rank-sink. </p>