Clone a graph -- Leetcode

Question:

Answer:

/**

 * Definition for undirected graph.

 * struct UndirectedGraphNode {

 *     int label;

 *     vector<UndirectedGraphNode *> neighbors;

 *     UndirectedGraphNode(int x) : label(x) {};

 * };

 */

class Solution {

public:

    UndirectedGraphNode* dfs(UndirectedGraphNode *v, map<int, UndirectedGraphNode*> &visited){

        UndirectedGraphNode* res = new UndirectedGraphNode(v->label);

        visited[v->label]=res;

        for (int i=0;i<v->neighbors.size();i++){

            if (!visited[v->neighbors[i]->label]){

                res->neighbors.push_back(dfs(v->neighbors[i],visited));

            }else{

                res->neighbors.push_back(visited[v->neighbors[i]->label]);

            }

        }

        return res;

    }

    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {

        // IMPORTANT: Please reset any member data you declared, as

        // the same Solution instance will be reused for each test case.

        if (node==NULL){

            return NULL;

        }else{

            map<int, UndirectedGraphNode*> visited;

            UndirectedGraphNode* res = dfs(node, visited);

            return res;

        }

            

    }

};