HARD NC#60 Blind #65 Trees / DFS
297. Serialize and Deserialize Binary Tree
📖 Problem
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.
🧠 Visual Learning Aid
1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases
JS/TS Refreshers
- •Array methods (`push`, `pop`, `shift`, `slice`)
- •Object/Map/Set usage patterns
- •Function parameter and return typing
- •Recursive stack flow
- •Cycle prevention
- •Post-order reasoning
Logical Thinking Concepts
- •Define invariants before coding
- •Check edge cases first (`[]`, single element, duplicates)
- •Estimate time/space before implementation
- •Apply DFS reasoning pattern
- •Apply Recursion reasoning pattern
💡 Approach
- → Use preorder traversal for serialization
- → Use null markers for missing children
- → For deserialization, use recursion to rebuild tree
- → Time: O(n), Space: O(n)
🛠️ Hints & Pitfalls
Hints
- •Use preorder traversal for serialization
- •Use null markers for missing children
- •For deserialization, use recursion to rebuild tree
Common Pitfalls
- •Time: O(n), Space: O(n)
🧪 Test Cases
Hidden tests on submit: 1
Test Case 1
Not run Input:
preorder(node: TreeNode | null); Expected:
Computed from hidden reference Test Case 2
Not run Input:
preorder(node.left); Expected:
Computed from hidden reference Test Case 3
Not run Input:
preorder(node.right); Expected:
Computed from hidden reference 📝 Code Editor
📤 Output