133. 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 #.

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         / \         \_/

思路：DFS

 /** * Definition for undirected graph. * class UndirectedGraphNode { *     int label; *     List<UndirectedGraphNode> neighbors; *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); } * }; */public class Solution {    Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {        if (node == null)            return null;        if (map.containsKey(node))            return map.get(node);        UndirectedGraphNode newHead = new UndirectedGraphNode(node.label);        map.put(node, newHead);        for (UndirectedGraphNode aNeighbor : node.neighbors)            newHead.neighbors.add(cloneGraph(aNeighbor));        return newHead;    }}