LeetCode - Clone Graph

CloneGraph.java

//DFS
public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<>();
        return helper(node, map);
    }
    
private UndirectedGraphNode helper(UndirectedGraphNode node, HashMap<UndirectedGraphNode, UndirectedGraphNode> map){
        if(node == null) return node;
        if(map.containsKey(node)) return map.get(node); 
        UndirectedGraphNode copyNode = new UndirectedGraphNode(node.label);
        map.put(node, copyNode); 
        for(UndirectedGraphNode nbnode : node.neighbors){
            copyNode.neighbors.add(helper(nbnode, map));
        }
        return copyNode;
}
 
 // Another version of DFS
 public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        if(node == null) return node;
        HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<>();
        UndirectedGraphNode copyNode = new UndirectedGraphNode(node.label);
        map.put(node, copyNode);
        helper(node, map);
        return map.get(node);
    }
    
    private void helper(UndirectedGraphNode node, HashMap<UndirectedGraphNode, UndirectedGraphNode> map){
        if(node == null) return;
        for(UndirectedGraphNode nbnode : node.neighbors){
            if(!map.containsKey(nbnode)){
                UndirectedGraphNode temp = new UndirectedGraphNode(nbnode.label);
                map.put(nbnode, temp);
                map.get(node).neighbors.add(temp);
                helper(nbnode, map);
            } else {
                map.get(node).neighbors.add(map.get(nbnode));
            }
        }
    }
    
// BFS
public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        if(node == null) return null;
        HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
        Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
        queue.offer(node);
        UndirectedGraphNode copyNode = new UndirectedGraphNode(node.label);
        map.put(node, copyNode);
        while(!queue.isEmpty()){
            UndirectedGraphNode Node = queue.poll();
            copyNode = map.get(Node);
            for(UndirectedGraphNode neighbor : Node.neighbors){
                if(!map.containsKey(neighbor)){
                    UndirectedGraphNode copyNeighbor = new UndirectedGraphNode(neighbor.label);
                    copyNode.neighbors.add(copyNeighbor);
                    map.put(neighbor, copyNeighbor);
                    queue.offer(neighbor);
                }else{
                    copyNode.neighbors.add(map.get(neighbor));   // 
                }
            }
        }
        return map.get(node);
    }