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 {
public:
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) 
    {
        map<const UndirectedGraphNode*,UndirectedGraphNode*> nodemap;
        return copy(nodemap,node);
    }
    UndirectedGraphNode* copy(map<const UndirectedGraphNode*,UndirectedGraphNode*>& nodemap,UndirectedGraphNode *node)
    {
        if(node==NULL) return NULL;
        if(nodemap.find(node)!=nodemap.end()) return nodemap.find(node)->second;
        
        UndirectedGraphNode* root=new UndirectedGraphNode(node->label);
        nodemap[node]=root;
        
        for(int i=0;i<node->neighbors.size();i++)
        {
            root->neighbors.push_back(copy(nodemap,node->neighbors[i]));
        }
        return root;
    }
};