[Lintcode]Clone Graph

lone an undirected graph. Each node in the graph contains alabel and a list of its neighbors.

How we serialize an undirected graph:

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 node2.
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     / \     \_/

Have you met this question in a real interview? 

Yes

Example

return a deep copied graph.

关键是如何避免环和点。  此时可以使用额外的hashmap记录已经走过的点。如果走过了，直接从map中取出即可。

public class Solution {        Map<Integer, UndirectedGraphNode> map = new HashMap<Integer, UndirectedGraphNode>();    /**     * @param node: A undirected graph node     * @return: A undirected graph node     */    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {        if(node == null) return null;        UndirectedGraphNode tmp = new UndirectedGraphNode(node.label);        map.put(node.label, tmp);        ArrayList<UndirectedGraphNode> list = new ArrayList<UndirectedGraphNode>();        for(UndirectedGraphNode u : node.neighbors) {            if(map.containsKey(u.label)) {                tmp.neighbors.add(map.get(u.label));            }            else {                tmp.neighbors.add(cloneGraph(u));            }        }        return tmp;    }}