Lowest Common Ancestor of a BST — C# Coding Problem
Difficulty: medium | Category: tree
Problem Description
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: '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).' **Insight:** In a BST, if both `p` and `q` are smaller than `root`, the LCA is in the left subtree. If both are larger, it's in the right subtree. Otherwise, `root` is the LCA.
Examples
Example 1
Input: root = [6,2,8,0,4,7,9], p = 2, q = 8
Output: 6
Example 2
Input: root = [6,2,8,0,4,7,9], p = 2, q = 4
Output: 2