Well, I have some doubt about the graph representation in this problem, though it might not affect the solution to this problem. In this problem, we are asked to clone a undirected graph, which means for the pair of connected nodes, each one should be presented in the other's neighbors list.

- For example: if there are two nodes 0 and 1 in a graph, and they are

connected to each other, then the graph representation should be

{0,1#1,0} - So the test case in this problem, the graph

{0,1,2#1,2#2,2} should be regarded as a directed graph.

As said before, the solution might not be affected no matter what the representation is, but I don't want to be confused by the understanding of graph representation. So tell me if my understanding is wrong. Thanks!