Clone Graph [LeetCode]

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
         / \
         \_/

Summary: BFS, one queue for BFS, one map for visited nodes,  one map for mapping between original nodes and the nodes of new graph.

 /**
  * 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;
         vector<UndirectedGraphNode *> node_queue;
         map<UndirectedGraphNode *, bool> visited;
         map<UndirectedGraphNode *, UndirectedGraphNode *> node_map;
         UndirectedGraphNode * root = new UndirectedGraphNode(node->label);
         node_map[node] = root;
         visited[node] = true;
         node_queue.push_back(node);

         while(node_queue.size() > ){
             UndirectedGraphNode * node = node_queue[];
             node_queue.erase(node_queue.begin());
             UndirectedGraphNode * new_node = node_map[node];
             for(auto item : node->neighbors){
                 if(visited.find(item) != visited.end()){
                     new_node->neighbors.push_back(node_map[item]);
                 }else{
                     node_queue.push_back(item);
                     UndirectedGraphNode * new_item = new UndirectedGraphNode(item->label);
                     node_map[item] = new_item;
                     new_node->neighbors.push_back(new_item);
                     visited[item] = true;
                 }
             }
         }

         return root;
     }
 };