Design an algorithm to serialize and deserialize a binary tree.

• String serialize(TreeNode root) — encodes the tree to a string.
• TreeNode deserialize(String data) — decodes the string back to the tree.

There is no restriction on your serialization/deserialization algorithm.

Example:

Input: root = [1,2,3,null,null,4,5]
Output: [1,2,3,null,null,4,5]