I am trying to learn 2-SAT. All I found is a google translated e-maxx.ru and a wekipedia page. But I could not understand all of them. I understand the graph construction and the impossible case, why and when it does not have solution. its clear to me . But I can not understand the topo sort / start time finish time part inside it. What else information can we extract form 2-SAT besides satisfiable/not?

• http://mirror.codeforces.com/problemset/problem/228/E
• I found this problem as an exercise of 2-SAT. As i mentioned I understand the graph construction and decision part but I can not understand the topo sort part for path printing (the order that ons all bits).