leetcode--Clone Graph

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

/**
 * Definition for undirected graph.
 * class UndirectedGraphNode {
 *     int label;
 *     ArrayList<UndirectedGraphNode> neighbors;
 *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 * };
 */
public class Solution {
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        UndirectedGraphNode newNode = null;
        if(node != null){
            Map<UndirectedGraphNode, UndirectedGraphNode> org = new HashMap<UndirectedGraphNode,UndirectedGraphNode>();
            ArrayList<UndirectedGraphNode> alist = new ArrayList<UndirectedGraphNode>();
            alist.add(node);
            for(int i = 0; i < alist.size(); ++i){
                UndirectedGraphNode temp = alist.get(i);
                UndirectedGraphNode cloneNode = null;
                if(!org.containsKey(temp)){
                    cloneNode = new UndirectedGraphNode(temp.label);
                    org.put(temp, cloneNode);
                }
                else
                    cloneNode = org.get(temp);                    
                List<UndirectedGraphNode> nei = temp.neighbors;
                for(int j = 0; j < nei.size(); ++j){
                    if(org.containsKey(nei.get(j)))
                        cloneNode.neighbors.add(org.get(nei.get(j)));
                    else{
                        UndirectedGraphNode clNode = new UndirectedGraphNode(nei.get(j).label);
                        alist.add(nei.get(j));
                        org.put(nei.get(j), clNode);
                        cloneNode.neighbors.add(clNode);
                    }                            
                }
            }
            newNode = org.get(node);
        }
        return newNode;
    }
}