98. Validate Binary Search Tree D&C or Inorder Traverse

D&C:

# 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 Result:
    def __init__(self, maxval = float("-inf"), minval = float("inf"), isBST = True):
        self.maxval = maxval
        self.minval = minval
        self.isBST = True
class Solution:
    #divide and conquer 
    def isValidBST(self, root: TreeNode) -> bool:
        ans = self.helper(root)
        return ans.isBST
    def helper(self, root: TreeNode) -> Result:
        if root == None:
            return Result()
        left = self.helper(root.left)
        right = self.helper(root.right)
        result = Result()
        result.isBST = left.maxval < root.val < right.minval and left.isBST and right.isBST
        result.maxval = max(left.maxval, right.maxval, root.val)
        result.minval = min(left.minval, right.minval, root.val)
        return result

Inorder:

# 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 Result:
    def __init__(self, maxval = float("-inf"), minval = float("inf"), isBST = True):
        self.maxval = maxval
        self.minval = minval
        self.isBST = True
class Solution:
    #Inorder
    currentVal = float("-inf")
    def isValidBST(self, root: TreeNode) -> bool:
        if root == None:
            return True
        if not (self.isValidBST(root.left)):
            return False
        if self.currentVal >= root.val:
            return False
        self.currentVal = root.val
        if not self.isValidBST(root.right):
            return False
        return True