图|LeetCode 133. Clone Graph（克隆图）哈希|哈希映射|克隆

原题网址：https://leetcode.com/problems/clone-graph/
【图|LeetCode 133. Clone Graph（克隆图）】
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:

1 / \ /\ 0 --- 2 / \ \_/

方法：使用哈希映射保存已克隆的节点。

/** * Definition for undirected graph. * class UndirectedGraphNode { *int label; *List neighbors; *UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList(); } * }; */ public class Solution { private Map map = new HashMap<>(); public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) { if (node == null) return null; UndirectedGraphNode cloned = map.get(node.label); if (cloned != null) return cloned; cloned = new UndirectedGraphNode(node.label); map.put(cloned.label, cloned); for(UndirectedGraphNode neighbor: node.neighbors) { cloned.neighbors.add(cloneGraph(neighbor)); } return cloned; } }