Description:
Clone an undirected graph. Each node in the graph contains a label and a list of its neighbours.
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 neighbour 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
/ \
\_/
算法分析：
深度優先和廣度優先都可以解決這個問題
代碼如下：
DFS
// LeetCode, Clone Graph
class Solution {
public:
UndirectedGraphNode *cloneGraph(const UndirectedGraphNode *node) {
if(node == nullptr) return nullptr;
// key is original node