Problem Clone Graph

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Problem Description:

Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.

Solution:

 1     public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) { 2         if (node == null) { 3             return null; 4         } 5         Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>(); 6         Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>(); 7         queue.add(node); 8         while (!queue.isEmpty()) { 9             UndirectedGraphNode q = queue.poll();10             UndirectedGraphNode newNode = new UndirectedGraphNode(q.label);11             map.put(q, newNode);12             for (UndirectedGraphNode neighbor : q.neighbors) {13                 if (!map.containsKey(neighbor)) {14                     queue.add(neighbor);15                 }16             }17         }18         Set<UndirectedGraphNode> keySet = map.keySet();19         for (UndirectedGraphNode p : keySet) {20             UndirectedGraphNode n  = map.get(p);21             for (UndirectedGraphNode q : p.neighbors) {22                 n.neighbors.add(map.get(q));23             }24         }25 26         return map.get(node);27     }