Serialize and Deserialize N-ary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize an N-ary tree. An N-ary tree is a rooted tree in which each node has no more than N children. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that an N-ary tree can be serialized to a string and this string can be deserialized to the original tree structure.

For example, you may serialize the following 3-ary tree

as [1 [3[5 6] 2 4]]. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Note:

1. N is in the range of [1, 1000]
2. Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

分析：下面这种方法

 /*
 // Definition for a Node.
 class Node {
     public int val;
     public List<Node> children;

     public Node() {}

     public Node(int _val,List<Node> _children) {
         val = _val;
         children = _children;
     }
 };
 */
 class Codec {

     // Encodes a tree to a single string.
     public String serialize(Node root) {
         if (root == null) return "";

         Queue<Node> que = new LinkedList<>();
         StringBuilder sb = new StringBuilder();
         sb.append(Integer.toString(root.val)).append(",#,");
         que.add(root);

         while (!que.isEmpty()) {
             Node node = que.poll();
             for (Node n : node.children) {
                 sb.append(Integer.toString(n.val)).append(",");
                 que.add(n);
             }
             sb.append("#,");
         }

         return sb.toString();
     }

     // Decodes your encoded data to tree.
     public Node deserialize(String data) {
         if (data.length() == ) return null;
         String[] s = data.split(",");

         Queue<Node> que = new LinkedList<>();
         Node root = new Node(Integer.parseInt(s[]), new ArrayList<Node>());
         que.add(root);
         int i = ;

         while (!que.isEmpty()) {
             Node node = que.poll();
             i++;
             while (!s[i].equals("#")) {
                 Node c = new Node(Integer.parseInt(s[i]), new ArrayList<>());
                 node.children.add(c);
                 que.add(c);
                 i++;
             }
         }

         return root;
     }
 }

 // Your Codec object will be instantiated and called as such:
 // Codec codec = new Codec();
 // codec.deserialize(codec.serialize(root));