http://discuss.codechef.com/questions/26248/kmhamha-editorial

I am reading this editorial for solving vertex cover problem for bipartite graph. I am getting problem in a line where he divide edges in two set of vertex to reduce problem to a bipartite graph.

For example, if we have 4 demons standing at (1, 8), (5, 6), (3, 8), (5, 4), we will end with the following bipartite graph:

R = {1, 3, 5}

C = {4, 6, 8}

E = {(1, 8), (5, 6), (3, 8), (5, 4)}

What will happen if we have one more demon at position (4,6) ? Now how can we divide them into two different set of bipartite graph. Also how can we assign demon at position (0,0) in two set of bipartite graph.

Please help me to understand. Thanks! in advance.