Introduction

In this blog post, we will explore how to solve the LeetCode problem "449" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

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.

Explanation

Here's a solution for serializing and deserializing a Binary Search Tree (BST), focusing on efficiency and compactness.

• Serialization: Perform a preorder traversal of the BST, recording the node values into a string. Use a delimiter (e.g., comma) to separate the values. Represent None (empty nodes) with a special marker (e.g., '#').

• Deserialization: Use the serialized string to reconstruct the BST. The preorder traversal order allows us to create the root node first, then recursively build the left and right subtrees. Because it is a BST, we can efficiently find the correct position for each node during the building process.

• Complexity: Time Complexity: O(N) for both serialization and deserialization, where N is the number of nodes. Space Complexity: O(N) in the worst case (skewed tree) for both serialization and deserialization due to recursion stack and storing the serialized string/list.

Code

    class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

class Codec:

    def serialize(self, root):
        """Encodes a tree to a single string.

        :type root: TreeNode
        :rtype: str
        """
        def preorder(node):
            if not node:
                return ['#']
            return [str(node.val)] + preorder(node.left) + preorder(node.right)

        return ','.join(preorder(root))


    def deserialize(self, data):
        """Decodes your encoded data to tree.

        :type data: str
        :rtype: TreeNode
        """
        def build_bst(nodes):
            if not nodes:
                return None

            val = nodes.pop(0)
            if val == '#':
                return None

            root = TreeNode(int(val))
            root.left = build_bst(nodes)
            root.right = build_bst(nodes)
            return root

        nodes = data.split(',')
        return build_bst(nodes)