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) {
    	if (node == null) {
    		return null;
    	}
        Queue<UndirectedGraphNode> queue = new LinkedList<>();
        HashMap<UndirectedGraphNode,UndirectedGraphNode> hashMap = new HashMap<>();
        UndirectedGraphNode head = new UndirectedGraphNode(node.label);
        hashMap.put(node, head);
        queue.add(node);
        while (!queue.isEmpty()) {
        	UndirectedGraphNode poll = queue.poll();
        	for (UndirectedGraphNode uh : poll.neighbors) {
        		if (!hashMap.containsKey(uh)) {
        			queue.add(uh);
        			UndirectedGraphNode tmp = new UndirectedGraphNode(uh.label);
        			hashMap.put(uh, tmp);
        		}
        		hashMap.get(poll).neighbors.add(hashMap.get(uh));
        	}
        }
        return head;
    }
}