binary_search_tree.py

class binarytree:
    def __init__(self, val):
        self.val = val
        self.leftnode = leftnode
        self.rightnode = rightnode
import sys
class BinarySearchTree:
    def validate_BST(self, root: binarytree) -> bool:
        return self.valid(root, sys.maxsize, -sys.maxsize)
    def valid(self, root, max_, min_):
        if root == None:
            return True
        else:
            return False
        return self.valid(root.leftnode, root.val, min_) and self.valid(root.rightnode, max_, root.val)

Hi Aman, thank you for the 120 Python Projects. They are highly encouraging to keep learning.

In this solution there is no validation on the value structure of the Binary tree: left < root < right.

I believe the solution I propose works

    def valid(self, root, max_, min_):
        if root == None:
            return True
        else:
            if root.val > min_ and root.val < max_:
                return self.valid(root.leftnode, root.val, min_) and self.valid(root.rightnode, max__, root.val)
            else:
                return False

Thank you again por posting the projects