133. Clone Graph

/*图的复制，考虑到一点就是如果label相同时认为是同一节点，环的存在，因此是不可以再new，为了保证时间，用hashmap会比较快 */Map<Integer,UndirectedGraphNode> hashMap=new HashMap();public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {    if(node==null)return null;    if(hashMap.containsKey(node.label)){        return hashMap.get(node.label);    }    UndirectedGraphNode clone=new UndirectedGraphNode(node.label);    hashMap.put(node.label,clone);    for(UndirectedGraphNode gn:node.neighbors){        clone.neighbors.add(cloneGraph(gn));    }    return clone;}