26. Serialize and Deserialize Binary Tree

Implement two functions:

1. serialize - Convert a binary tree to a string
2. deserialize - Convert a string back to a binary tree

Given a binary tree node structure, serialize it to a string format and then deserialize it back to reconstruct the original tree.

Requirements

1. Serialization

• Convert binary tree to string representation
• Use a format that preserves tree structure
• Handle null nodes (missing children)
• Use comma-separated values or similar format

2. Deserialization

• Parse string back to binary tree
• Reconstruct exact same tree structure
• Handle null nodes correctly
• Maintain node values and relationships

Example Usage

// Tree structure:
//     1
//    / \
//   2   3
//      / \
//     4   5

const root = new TreeNode(1);
root.left = new TreeNode(2);
root.right = new TreeNode(3);
root.right.left = new TreeNode(4);
root.right.right = new TreeNode(5);

const serialized = serialize(root);
// "1,2,null,null,3,4,null,null,5,null,null"

const deserialized = deserialize(serialized);
// Reconstructs the original tree

Real-World Context

This problem models real data serialization scenarios:

• Data storage: Save tree structures to databases or files
• Network transmission: Send tree data over APIs
• Caching: Store tree structures for later reconstruction
• State management: Serialize application state trees