[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
         / 
         \_/

DFS!

/**
 * Definition for undirected graph.
 * struct UndirectedGraphNode {
 *     int label;
 *     vector<UndirectedGraphNode *> neighbors;
 *     UndirectedGraphNode(int x) : label(x) {};
 * };
 */
class Solution {
public:
    void cloneNode(UndirectedGraphNode *&res, UndirectedGraphNode *node, map<int, UndirectedGraphNode*> &mp) {
        if (mp[node->label] != NULL) {
            res = mp[node->label];
            return;
        }
        res = new UndirectedGraphNode(node->label);
        res->neighbors.resize(node->neighbors.size());
        mp[node->label] = res;

        for (int i = 0; i < node->neighbors.size(); ++i) {
            cloneNode(res->neighbors[i], node->neighbors[i], mp);
        }
    }
    
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
        if (node == NULL) return NULL;
        map<int, UndirectedGraphNode*> mp;
        UndirectedGraphNode* res; 
        cloneNode(res, node, mp);
        return res;
    }
};