Leetcode -- Clone Graph

This is a simple question. Just use a map to log whether the node was copied. I made a mistake by putting hash.emplace(node, clonedNode); after the for loop, this will cause infinite loop.

 /**  
  * Definition for undirected graph.  
  * struct UndirectedGraphNode {  
  *   int label;  
  *   vector<UndirectedGraphNode *> neighbors;  
  *   UndirectedGraphNode(int x) : label(x) {};  
  * };  
  */  
 class Solution {  
 public:  
   UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {  
     unordered_map<UndirectedGraphNode *, UndirectedGraphNode *> hash;  
     if(node == NULL) {  
       return NULL;  
     }  
     return cloneGraphHelper(node, hash);  
   }  
   UndirectedGraphNode * cloneGraphHelper(UndirectedGraphNode *node, unordered_map<UndirectedGraphNode *, UndirectedGraphNode *>& hash) {  
     if(hash.count(node) > 0) {  
       return hash[node];  
     }   
     UndirectedGraphNode * clonedNode = new UndirectedGraphNode(node->label);  
     hash.emplace(node, clonedNode);   // made mistake here
     vector<UndirectedGraphNode *> neighbors;  
     for(UndirectedGraphNode * neighbor : node->neighbors) {  
       UndirectedGraphNode * cloneNeighbor = cloneGraphHelper(neighbor, hash);  
       neighbors.emplace_back(cloneNeighbor);  
     }  
     swap(clonedNode->neighbors,neighbors);  
     return clonedNode;  
   }  
 };  

Slightly modifid

 /**  
  * Definition for undirected graph.  
  * struct UndirectedGraphNode {  
  *   int label;  
  *   vector<UndirectedGraphNode *> neighbors;  
  *   UndirectedGraphNode(int x) : label(x) {};  
  * };  
  */  
 class Solution {  
 public:  
   UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {  
     if(node == NULL) {  
       return NULL;  
     }  
     unordered_map<UndirectedGraphNode *, UndirectedGraphNode *> hash;  
     return cloneGraph(node, hash);  
   }  
   UndirectedGraphNode * cloneGraph(UndirectedGraphNode* node, unordered_map<UndirectedGraphNode *, UndirectedGraphNode *>& hash) {  
     if(hash.count(node) > 0) {  
       return hash[node];  
     }   
       UndirectedGraphNode * cloneNode = new UndirectedGraphNode(node->label);  
       hash.emplace(node, cloneNode);  
       for(UndirectedGraphNode * neighbor : node->neighbors) {  
         cloneNode->neighbors.emplace_back(cloneGraph(neighbor, hash));  
       }  
       return cloneNode;  
   }  
 };