Clone Graph

Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.

public class Solution {
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        if(node==null) return node;
        UndirectedGraphNode n1 = new UndirectedGraphNode(node.label);
        HashMap<UndirectedGraphNode,UndirectedGraphNode> map = new HashMap<UndirectedGraphNode,UndirectedGraphNode>();
        map.put(node,n1);
        LinkedList<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
        queue.offer(node);
        while(!queue.isEmpty()){
            UndirectedGraphNode original = queue.poll();
            ArrayList<UndirectedGraphNode> ons =  original.neighbors;
            for(int i=0;i<ons.size();i++){
                UndirectedGraphNode on = ons.get(i);
                if(!map.containsKey(on)){
                    queue.offer(on);
                    UndirectedGraphNode clone = new UndirectedGraphNode(on.label);
                    map.get(original).neighbors.add(clone);
                    map.put(on,clone);
                }
                else{
                    map.get(original).neighbors.add(map.get(on));
                }
            }
        }
        return n1;
    }
}