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         / \         \_/

 

直接用HashMap来做应该是最简单的，这个对十字链表也可以。使用hashmap来存储node的对应关系。

1 /** 2  * Definition for undirected graph. 3  * class UndirectedGraphNode { 4  *     int label; 5  *     ArrayList
           
             neighbors; 6  *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList
            
             (); } 7  * }; 8  */ 9 public class Solution {10     HashMap
             
               map = new HashMap
              
               ();11     public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {12         map.clear();13         return cloneNode(node);14     }15      16     private UndirectedGraphNode cloneNode(UndirectedGraphNode node)17     {18         if (node == null) return null;19         if (map.containsKey(node)) return map.get(node);20         else21         {22             UndirectedGraphNode copy = new UndirectedGraphNode(node.label);23             map.put(node, copy);24             for (UndirectedGraphNode n : node.neighbors)25             {26                 copy.neighbors.add(cloneNode(n));27             }28             return copy;29         }30     }31 }