CODE 130: Clone Graph

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 #.

1. First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node is labeled as 1. Connect node 1 to node 2.
3. 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
         / \
         \_/

	public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
		// IMPORTANT: Please reset any member data you declared, as
		// the same Solution instance will be reused for each test case.
		if (null == node) {
			return null;
		}
		Map<Integer, UndirectedGraphNode> visitTable = new HashMap<Integer, UndirectedGraphNode>();
		return clone(node, visitTable);
	}

	protected UndirectedGraphNode clone(UndirectedGraphNode node,
			Map<Integer, UndirectedGraphNode> table) {
		if (node == null)
			return null;

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

		UndirectedGraphNode newnode = new UndirectedGraphNode(node.label);
		table.put(newnode.label, newnode);

		for (int i = 0; i < node.neighbors.size(); i++) {
			UndirectedGraphNode neighbor = clone(node.neighbors.get(i), table);
			newnode.neighbors.add(neighbor);
		}

		return newnode;
	}