133 Clone Graph

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) {
        if (!node)
            return NULL;
        unordered_map<int,UndirectedGraphNode*> mp;
        return help(node,mp);
    }
    UndirectedGraphNode* help(UndirectedGraphNode *node,unordered_map<int,UndirectedGraphNode*> &mp)
    {
        if (mp.find(node->label)==mp.end())
        {
            UndirectedGraphNode *newNode = new UndirectedGraphNode(node->label);
            mp[node->label]=newNode;
            for (int i=0;i<node->neighbors.size();i++){
                newNode->neighbors.push_back(help(node->neighbors[i],mp));
            }
        }
        return mp[node->label];
    }
};