graph - Source and Sink in DAGs -


consider graph g dag. prove in graph g', obtained reversing edges of g, source(s)/sink(s) in g become sink(s)/source(s) respectively.

i can see i'm quite unable give formal proof it. me out. :')

by definition vertex indegree 0 called source , vertex outdegree 0 called sink.

reversing edges, indegree , outdegree interchanged each vertex. means if vertex v in g have indegree d1 , outdegree d2, v in g' has indegree d2 , outdegree d1.

vertex v source in g <=> v has indegree 0 in g <=> v has outdegree 0 in g' <=> v sink in g'.


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