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/**

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

*

*

* OJ's undirected graph serialization:

* Nodes are labeled uniquely.

*

* We use # as a separator for each node, and , as a separator for node label and each neighbor of the node.

* As an example, consider the serialized graph {0,1,2#1,2#2,2}.

*

* The graph has a total of three nodes, and therefore contains three parts as separated by #.

*

* First node is labeled as 0. Connect node 0 to both nodes 1 and 2.

* Second node is labeled as 1. Connect node 1 to node 2.

* Third node is labeled as 2. Connect node 2 to node 2 (itself), thus forming a self-cycle.

* Visually, the graph looks like the following:

*

* 1

* / \

* / \

* 0 --- 2

* / \

* \_/

*

*/

/**

* Definition for undirected graph.

* class UndirectedGraphNode {

* int label;

* List<UndirectedGraphNode> neighbors;

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

* };

*/

public class CloneGraph133 {

public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {

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

return clone(node, map);

}

private UndirectedGraphNode clone(UndirectedGraphNode node, HashMap<Integer, UndirectedGraphNode> map) {

if (node == null) return null;

if (map.containsKey(node.label)) {

return map.get(node.label);

}

UndirectedGraphNode clone = new UndirectedGraphNode(node.label);

map.put(clone.label, clone);

for (UndirectedGraphNode neighbor : node.neighbors) {

clone.neighbors.add(clone(neighbor, map));

}

return clone;

}

}