singularity

singularity 🔎

235. ✅ Lowest Common Ancestor of a Binary Search Tree

O(h)

# 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':
        lca = [root]

        def search(root):
            if not root:
                return
                
            lca[-1] = root

            if root is p or root is q:
                return
            
            elif root.val < p.val and root.val < q.val:
                search(root.right)
            elif root.val > p.val and root.val > q.val:
                search(root.left)
            else:
                return

        search(root)
        return lca[-1]