Lowest Common Ancestor of a Binary Search Tree

Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in the BST. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes `p` and `q` as the lowest node in `T` that has both `p` and `q` as descendants (where we allow **a node to be a descendant of itself**).”   **Example 1:** **Input:** root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 8 **Output:** 6 **Explanation:** The LCA of nodes 2 and 8 is 6. ``` **Example 2:** **Input:** root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 4 **Output:** 2 **Explanation:** The LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition. ``` **Example 3:** **Input:** root = [2,1], p = 2, q = 1 **Output:** 2 ```   **Constraints:** - The number of nodes in the tree is in the range `[2, 105]`. - `-109 <= Node.val <= 109` - All `Node.val` are **unique**. - `p != q` - `p` and `q` will exist in the BST.