public UndirectedGraphNode cloneGraphB(UndirectedGraphNode node){
  Map<Integer,UndirectedGraphNode> map=new HashMap<>();
  return dfs(node,map);
}

public UndirectedGraphNode cloneGraphB ( UndirectedGraphNode node ) { Map < Integer , UndirectedGraphNode > map = new HashMap < > ( ) ; return dfs ( node , map ) ; }
dfs . pass the node and map to its neighbors . add neighbors dfs result to its neighbors and return .
