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

CloneGraph.java

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 clonedNode = new UndirectedGraphNode(node.label);
	map.put(clonedNode.label, clonedNode);
	for(UndirectedGraphNode neighbor : node.neighbors)
		clonedNode.neighbors.add(cloneGraph(neighbor));

	return clonedNode;
}