[LeetCode]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
         / 
         \_/

/**
 * Definition for undirected graph.
 * struct UndirectedGraphNode {
 *     int label;
 *     vector<UndirectedGraphNode *> neighbors;
 *     UndirectedGraphNode(int x) : label(x) {};
 * };
 */
class Solution {
private:
    map<int,UndirectedGraphNode *> m;
public:
    UndirectedGraphNode *DFS(UndirectedGraphNode *node)
    {
        if(node==NULL) return NULL;
        if(m.find(node->label)!=m.end()) return m[node->label];
        UndirectedGraphNode *newNode=new UndirectedGraphNode(node->label);
        m[newNode->label]=newNode;
        for(vector<UndirectedGraphNode *>::iterator it=node->neighbors.begin();it!=node->neighbors.end();it++)
        {
            UndirectedGraphNode *newNeighbor=DFS(*it);
            newNode->neighbors.push_back(newNeighbor);
        }
        return newNode;
    }
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
        return DFS(node);
    }
};