Is Serialize and Deserialize BST easy or hard?

Serialize and Deserialize BST is considered a medium-level problem. The serialization step is straightforward, but the challenge lies in reconstructing the BST efficiently using traversal order and value constraints.

Serialize and Deserialize BST Python/Java solution

Python and C++ solutions commonly use preorder traversal with recursion and value bounds. Java and JavaScript implementations often demonstrate level-order traversal using a queue. Both approaches achieve O(n) time complexity while reconstructing the exact tree structure.

How to solve Serialize and Deserialize BST in O(n)?

Traverse the BST using preorder and store values in sequence. During deserialization, rebuild the tree by reading values and enforcing lower and upper bounds for each subtree. Because each value is processed once and inserted in the correct position immediately, the entire process runs in linear time.

What is the best approach for Serialize and Deserialize BST?

The most efficient approach uses preorder traversal with BST value bounds. Serialize the tree by recording nodes in preorder, then reconstruct it by inserting values within valid min/max ranges. This leverages BST ordering and avoids storing null markers, keeping both time and space complexity at O(n).

Is Serialize and Deserialize BST asked at Google/Amazon/Meta?

Tree serialization problems frequently appear in interviews at companies like Google, Amazon, and Meta. Variations such as Serialize and Deserialize Binary Tree or BST test understanding of traversal, recursion, and data structure design.

What data structure is used in Serialize and Deserialize BST?

The solution typically uses recursion with preorder traversal for DFS-based reconstruction or a queue for BFS level-order traversal. The BST property is critical for the optimized preorder approach because it allows reconstruction using value ranges.

What is the time complexity of Serialize and Deserialize BST?

Both serialization and deserialization run in O(n) time where n is the number of nodes. Each node is processed exactly once during traversal and reconstruction. Space complexity is O(n) due to the output string and recursion or queue storage.

Description Solution Video 14:27

449. Serialize and Deserialize BST

Medium60.1% acceptance4 companies

Serialization is 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 search tree. There is no restriction on how your serialization/deserialization algorithm should work. You need to ensure that a binary search tree can be serialized to a string, and this string can be deserialized to the original tree structure.

The encoded string should be as compact as possible.

Example 1:

Input: root = [2,1,3]
Output: [2,1,3]

Example 2:

Input: root = []
Output: []

Constraints:

The number of nodes in the tree is in the range [0, 10⁴].
0 <= Node.val <= 10⁴
The input tree is guaranteed to be a binary search tree.

Asked at 4 companies

Shopee Amazon Microsoft

Google

Topics

14:27

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Similar problems

Serialize and Deserialize Binary TreeHard Find Duplicate SubtreesMedium Serialize and Deserialize N-ary TreeHard

LanguageLoading editor…

1# Definition for a binary tree node.
2# class TreeNode:
3#     def __init__(self, x):
4#         self.val = x
5#         self.left = None
6#         self.right = None
7 
8class Codec:
9 
10    def serialize(self, root: Optional[TreeNode]) -> str:
11        """Encodes a tree to a single string.
12        """
13        
14 
15    def deserialize(self, data: str) -> Optional[TreeNode]:
16        """Decodes your encoded data to tree.
17        """
18        
19 
20# Your Codec object will be instantiated and called as such:
21# Your Codec object will be instantiated and called as such:
22# ser = Codec()
23# deser = Codec()
24# tree = ser.serialize(root)
25# ans = deser.deserialize(tree)
26# return ans

Starter codePython 3Spaces: 4

Examples

Case 1Case 2

Input

[2,1,3]

Input

[]

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