Add solution for 235. Lowest Common Ancestor of a Binary Search Tree

Author: sbk1014

lowest-common-ancestor-of-a-binary-search-tree/bhyun-kim.py

@@ -0,0 +1,36 @@
+"""
+235. Lowest Common Ancestor of a Binary Search Tree
+https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/
+"""
+
+# Definition for a binary tree node.
+class TreeNode:
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+"""
+Solution:
+    - If both p and q are greater than the root, the lowest common ancestor is in the right subtree.
+    - If both p and q are less than the root, the lowest common ancestor is in the left subtree.
+    - Otherwise, the root is the lowest common ancestor.
+
+Time complexity: O(N)
+    - The function is called recursively for each node
+Space complexity: O(N)
+    - Maximum depth of the recursion is the height of the tree
+"""
+
+class Solution:
+    def lowestCommonAncestor(
+        self, root: "TreeNode", p: "TreeNode", q: "TreeNode"
+    ) -> "TreeNode":
+        
+        if p.val > root.val and q.val > root.val:    
+            return self.lowestCommonAncestor(root.right, p, q)
+    
+        elif p.val < root.val and q.val < root.val:    
+            return self.lowestCommonAncestor(root.left, p, q)
+        else:
+            return root