Problem

Meta uses tree-shaped data in several internal systems, and a common task is converting a binary tree into a transportable string and reconstructing it later. Implement serialization and deserialization for a binary tree so that the rebuilt tree is structurally identical to the original.

Formal Specification

Implement a function serialize_deserialize(root) that:

• takes root, the root node of a binary tree represented as nested dictionaries with keys val, left, and right, or null
• returns an object with two fields:
  • serialized: a string encoding of the tree
  • deserialized: the reconstructed tree in the same nested dictionary format

Use level-order traversal. Represent missing children with the marker #, and separate tokens with commas.

Examples

Example 1 Input: root = {"val":1,"left":{"val":2,"left":null,"right":null},"right":{"val":3,"left":{"val":4,"left":null,"right":null},"right":{"val":5,"left":null,"right":null}}}

Output: {"serialized":"1,2,3,#,#,4,5,#,#,#,#","deserialized":same tree}

Explanation: The string preserves both values and null positions, so the original structure can be rebuilt exactly.

Example 2 Input: root = null

Output: {"serialized":"#","deserialized":null}

Explanation: An empty tree is encoded as a single null marker.

Constraints

• Number of nodes is in the range [0, 10^4]
• -1000 <= node.val <= 1000
• Node values may repeat
• The output tree must match the original structure and values exactly