133. Clone Graph

 1 /**
 2  * Definition for undirected graph.
 3  * class UndirectedGraphNode {
 4  *     int label;
 5  *     List<UndirectedGraphNode> neighbors;
 6  *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 7  * };
 8  */
 9 public class Solution {
10     public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
11         if (node == null) return null;
12         
13         Map<UndirectedGraphNode, UndirectedGraphNode> graphMap = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
14         Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
15         
16         queue.offer(node);
17         // create copy of new nodes
18         while (!queue.isEmpty()) {
19             UndirectedGraphNode n = queue.poll();
20             if (!graphMap.containsKey(n)) {
21                 UndirectedGraphNode copy = new UndirectedGraphNode(n.label);
22                 graphMap.put(n, copy);
23             }
24             for (UndirectedGraphNode neighbor: n.neighbors) {
25                 if (!graphMap.containsKey(neighbor)) {
26                     queue.offer(neighbor);
27                 }
28             }
29         }
30         // build neighbors
31         for (Map.Entry<UndirectedGraphNode, UndirectedGraphNode> entry: graphMap.entrySet()) {
32             UndirectedGraphNode original = entry.getKey();
33             UndirectedGraphNode copy = entry.getValue();
34             for (UndirectedGraphNode neighbor: original.neighbors) {
35                 copy.neighbors.add(graphMap.get(neighbor));
36             }
37         }
38         return graphMap.get(node);
39     }
40 }