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:
    void cloneGraph_core(UndirectedGraphNode *node, UndirectedGraphNode* &res, unordered_map<UndirectedGraphNode*, UndirectedGraphNode*>& originToCopy)
    {
        if(originToCopy[node])
            res = originToCopy[node];
        else
        {
            res = new UndirectedGraphNode(node->label);
            originToCopy[node] = res;
        }

        int len = node->neighbors.size();
        if(res->neighbors.empty())
        for(int i = 0; i < len; i++)
        {
            res->neighbors.push_back(0);    
            cloneGraph_core(node->neighbors[i], res->neighbors.back(), originToCopy);       
        }

    }
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) 
    {
        if(!node) return 0;
        unordered_map<UndirectedGraphNode*, UndirectedGraphNode*> originToCopy;

        UndirectedGraphNode *res;
        cloneGraph_core(node, res, originToCopy);       
        return res;
    }
};