class Solution {public:    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {        if (!node) return NULL;        UndirectedGraphNode *pRet = NULL;        queue<UndirectedGraphNode*> q;        unordered_map<int, UndirectedGraphNode *> map;                q.push(node);                while (!q.empty())        {            UndirectedGraphNode *p = q.front();            //    Create new node            UndirectedGraphNode *pNew = NULL;            if (map.find(p->label) == map.end())            {                pNew = new UndirectedGraphNode(p->label);                map[p->label] = pNew;                if (!pRet)    pRet = pNew;            }            else            {                pNew = map[p->label];            }            for (UndirectedGraphNode *pC : p->neighbors)            {                UndirectedGraphNode *pNewC = NULL;                if (map.find(pC->label) == map.end())                {                    pNewC = new UndirectedGraphNode(pC->label);                    map[pC->label] = pNewC;                    q.push(pC);                }                else                {                    pNewC = map[pC->label];                }                pNew->neighbors.push_back(pNewC);                            }            q.pop();        }        return pRet;    }};