Info
Make sure to say r is not None instead of just r, since 0 is also considered False in python
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def rec(self, node, l, r):
if (l is None) and (r is not None):
if node.val >= r:
return False
elif (r is None) and (l is not None):
if node.val <= l:
return False
elif l and r:
if not (l < node.val < r):
return False
if node.left:
if not self.rec(node.left, l, node.val):
return False
if node.right:
if not self.rec(node.right, node.val, r):
return False
return True
def isValidBST(self, root: Optional[TreeNode]) -> bool:
return self.rec(root, None, None)Validate Binary Search Tree 2023-02-06 10.43.42.excalidraw