Clone Graph [LeetCode]

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 #.

First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
Second node is labeled as 1. Connect node 1 to node 2.
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:

Summary: BFS, one queue for BFS, one map for visited nodes, one map for mapping between original nodes and the nodes of new graph.

 1 /**
 2  * Definition for undirected graph.
 3  * struct UndirectedGraphNode {
 4  *     int label;
 5  *     vector<UndirectedGraphNode *> neighbors;
 6  *     UndirectedGraphNode(int x) : label(x) {};
 7  * };
 8  */
 9 class Solution {
10 public:
11     UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
12         if(node == NULL)
13             return NULL;
14         vector<UndirectedGraphNode *> node_queue;
15         map<UndirectedGraphNode *, bool> visited;
16         map<UndirectedGraphNode *, UndirectedGraphNode *> node_map;
17         UndirectedGraphNode * root = new UndirectedGraphNode(node->label);
18         node_map[node] = root;
19         visited[node] = true;
20         node_queue.push_back(node);
21         
22         while(node_queue.size() > 0){
23             UndirectedGraphNode * node = node_queue[0];
24             node_queue.erase(node_queue.begin());
25             UndirectedGraphNode * new_node = node_map[node];
26             for(auto item : node->neighbors){
27                 if(visited.find(item) != visited.end()){
28                     new_node->neighbors.push_back(node_map[item]);
29                 }else{
30                     node_queue.push_back(item);
31                     UndirectedGraphNode * new_item = new UndirectedGraphNode(item->label);
32                     node_map[item] = new_item; 
33                     new_node->neighbors.push_back(new_item);
34                     visited[item] = true;
35                 }
36             }
37         }
38         
39         return root;
40     }
41 };