leetcode--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
         / \
         \_/

/**
 * Definition for undirected graph.
 * class UndirectedGraphNode {
 *     int label;
 *     List<UndirectedGraphNode> neighbors;
 *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 * };
 */
public class Solution {
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
		Map<UndirectedGraphNode,UndirectedGraphNode> map = 
				new HashMap<UndirectedGraphNode,UndirectedGraphNode>();
		if(node==null) return null;
		Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
		queue.add(node);
		UndirectedGraphNode root = new UndirectedGraphNode(node.label);
		map.put(node, root);
		while(!queue.isEmpty()){
			UndirectedGraphNode cur = queue.poll();		
			for(UndirectedGraphNode child:cur.neighbors){
				if(!map.containsKey(child)){
					UndirectedGraphNode p = new UndirectedGraphNode(child.label);
					map.put(child, p);
					queue.add(child);
				}
				map.get(cur).neighbors.add(map.get(child));
			}
		}
		return root;
    }
}