Serialize and Deserialize BST

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 a binary search tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary search tree can be serialized to a string and this string can be deserialized to the original tree structure.

The encoded string should be as compact as possible.

Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

 1 public class Codec {
 2     public String serialize(TreeNode root) {
 3         StringBuilder sb = new StringBuilder();
 4         serialize(root, sb);
 5         return sb.toString();
 6     }
 7     
 8     public void serialize(TreeNode root, StringBuilder sb) {
 9         if (root == null) return;
10         sb.append(root.val).append(",");
11         serialize(root.left, sb);
12         serialize(root.right, sb);
13     }
14 
15     // Decodes your encoded data to tree.
16     public TreeNode deserialize(String data) {
17         if (data.isEmpty()) return null;
18         Queue q = new LinkedList<>(Arrays.asList(data.split(",")));
19         return deserialize(q, Integer.MIN_VALUE, Integer.MAX_VALUE);
20     }
21     
22     public TreeNode deserialize(Queue q, int lower, int upper) {
23         if (q.isEmpty()) return null;
24         String s = q.peek();
25         int val = Integer.parseInt(s);
26         if (val < lower || val > upper) return null;
27         q.poll();
28         TreeNode root = new TreeNode(val);
29         root.left = deserialize(q, lower, val);
30         root.right = deserialize(q, val, upper);
31         return root;
32     }
33 }