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  . Connect node   to both nodes 

   1

    and 

   2

2. Second node is labeled as 

   1

   1

    to node 

   2

3. Third node is labeled as 

   2

   2

   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<UndirectedGraphNode> neighbors;
 6  *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 7  * };
 8  */
 9 public class Solution {
10     HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
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         else
21         {
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 }