title: Implementation issues in 2-Satisfiability problem
body: <p>I want to implement 2-SAT problem for 100000 literals. So there would be 200000 vertices. So I am stuck on having a array of all reachable vertices from each vertex, space complexity of   <code>O(200000^2)</code> which is infeasible So please suggest a solution for this. And please throw some light on efficient implementation of 2-SAT problem.</p>