[LeetCode]Clone Graph

[LeetCode]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 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
            / \
            \_/

   
   

   利用遞歸深搜，同時用一個map存儲已經 new 過的node，如果已經new 過則直接返回存在map裡的節點

   /**
    * Definition for undirected graph.
    * class UndirectedGraphNode {
    *     int label;
    *     List neighbors;
    *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList(); }
    * };
    */
   public class Solution {
   	Map map  = new HashMap<>();
   	public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
   		if (node == null)
   			return null;
   		if(map.containsKey(node)){
   			return map.get(node);
   		}
   		UndirectedGraphNode ug = new UndirectedGraphNode(node.label);
   		map.put(node, ug);
   		for (int i = 0; i < node.neighbors.size(); i++) {
   				ug.neighbors.add(cloneGraph(node.neighbors.get(i)));
   		}
   		return ug;
   	}
   }