Formal Semantics of Programming Languages

Hi everyone.

I'm trying to be prepare for my exam. Our professor gave us a list of problem for our review. I don't get the question below. Can someone help me please

Let X be a finite set. Can the set X x X be put in 1-1 correspondence with the set of all undirected graphs with vertex set X? Can the set X x X be put in 1-1 correspondence with the set of all directed graphs with vertex set X? For both cases, either show a correspondence or give a convincing argument that it cannot be accomplished.

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Thanks

Mark