Lowest Common Ancestor of a BST

Merge Two Sorted Lists

Binary Tree Level Order Traversal

Find the lowest shared ancestor of two values in a binary search tree.

Given a BST and two values present in it, return the value of their lowest common ancestor.

## Example
```json
Input: {"root":[6,2,8,0,4,7,9,null,null,3,5],"p":2,"q":8}
Output: 6
```

## Constraints
- 2 <= number of nodes <= 10000
- All node values are unique
- p and q exist in the tree

## Follow-up
How does BST ordering avoid a full tree traversal?

The key pattern is: BST ordering identifies where search paths split. Identify the state and invariant before coding.

Recognize the Pattern

Advance one state transition at a time. Mark or update state before exploring dependent work.

Build the Algorithm

Test empty or minimal input, skewed shapes, duplicates where allowed, and impossible outcomes.

Check Edge Cases

Time: O(h). Space: O(1).

Java/Go/Rust below are reference solutions for learning the pattern in those languages; only Python and JavaScript can be run and submitted for this problem, since the remote judge doesn't support the TreeNode structure yet.