Serialize and Deserialize Binary 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 a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary 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 tree

    1
   / \
  2   3
     / \
    4   5

as "[1,2,3,null,null,4,5]", just the same as how LeetCode OJ serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

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

Use any-order traversal to serialize the tree and then deserialize it. Note for serialization we cannot save any state so no global variable can be used. I convert the whole string to an iterator for deserialization.

public class Codec {
    // Encodes a tree to a single string.
     public String serialize(TreeNode root) {
        if (root == null)
            return "#,";
        return String.valueOf(root.val) + "," + serialize(root.left) + serialize(root.right);
    }
    

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        return getNode(Arrays.asList(data.substring(0, data.length() - 1).split(",")).iterator());
    }
    private TreeNode getNode(Iterator tree) {
        if (!tree.hasNext()) {
            return null;
        }
        String c = tree.next();
        if ("#".equals(c)) {
            return null;
        }
        TreeNode root = new TreeNode(Integer.parseInt(c));
        root.left = getNode(tree);
        root.right = getNode(tree);
        return root;
    }
}