import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

public class CloneGraph {

private Map<Integer, UndirectedGraphNode> map = new HashMap<>();

public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {

if(node == null) return null;

if(map.containsKey(node.label)) return map.get(node.label);

UndirectedGraphNode clone = new UndirectedGraphNode(node.label);

map.put(node.label, clone);

if(node.neighbors != null){

List<UndirectedGraphNode> neighbors = node.neighbors;

for(UndirectedGraphNode neighbor : neighbors){

clone.neighbors.add(cloneGraph(neighbor));

}

}

return clone;

}

}

class UndirectedGraphNode {

int label;

List<UndirectedGraphNode> neighbors;

UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }

}