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 #.

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         / \         \_/

深拷贝一个图，图可能有自环。

图中顶点的编号是unique的，利用这一点，可以在递归调用中识别已经copy的节点。

 HashMap<UndirectedGraphNode, Boolean> hashmap=new HashMap<>();HashMap<Integer, UndirectedGraphNode> newhashmap=new HashMap<>();public UndirectedGraphNode cloneGraph(UndirectedGraphNode node){if(node==null)return node;hashmap.put(node, true);UndirectedGraphNode newnode=new UndirectedGraphNode(node.label);newhashmap.put(newnode.label,newnode);for(UndirectedGraphNode tn : node.neighbors){if(!hashmap.containsKey(tn)){hashmap.put(tn, true);UndirectedGraphNode temp=cloneGraph(tn);newnode.neighbors.add(temp);}else{int lable=tn.label;newnode.neighbors.add(newhashmap.get(lable));}}return newnode;}