Clone Connected Graph Nodes without Sharing Original Objects

### Problem Given a node reference in a connected undirected graph, return the corresponding node reference in a deep copy of the graph. Each original node must have a separate new counterpart with the same value and corresponding cloned neighbors. The clone must not reuse original nodes. The supplied custom `Node` contains `int val` and `vector<Node*> neighbors`: ```cpp Node* cloneGraph(Node* node); ``` Adjacency lists below display the graph; they are not the function argument or return type. Neighbor collections are unordered. The starting node has value 1; display indices are one-based node labels. ### Examples ```text Original adjacency: [[2,3],[1,3],[1,2]] Clone adjacency: [[2,3],[1,3],[1,2]] ``` All three returned nodes are new objects, with the same triangle connectivity. ```text Original adjacency: [[]] Clone adjacency: [[]] ``` This is one isolated node, not an empty graph. ### Constraints - The graph has between 0 and 100 nodes; an empty input is null. - Node values are unique integers between 1 and 100. - There are no repeated edges or self-loops. - Every graph node is reachable from the supplied starting node.