Create Lowest-Common-Ancestor-of-a-Binary-Search-Tree.py

Author: AG-Systems

Leetcode/Lowest-Common-Ancestor-of-a-Binary-Search-Tree.py

@@ -0,0 +1,41 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
+        if root == None:
+            return None
+        if p.val < root.val and q.val > root.val:
+            return root
+        elif p.val > root.val and q.val < root.val:
+            return root
+        
+        def search(root, val, path):
+            if root == None:
+                return None
+            if root.val == val:
+                path.append(root)
+                return path
+            path.append(root)
+            if root.val > val:  
+                return search(root.left, val, path)
+            elif root.val < val:
+                return search(root.right, val, path)
+            
+        p_path = search(root, p.val, [])
+        q_path = search(root, q.val, [])
+        lca = None
+        while p_path and q_path:
+            p_node = p_path.pop(0)
+            q_node = q_path.pop(0)
+            if q_node.val == p_node.val:
+                lca = q_node
+            else:
+                break
+        return lca
+        
+