""" Node is defined as
class node:
  def __init__(self, data):
      self.data = data
      self.left = None
      self.right = None
"""

# Could've used inorder traversal and, every time a node is added to results array, check if it's actually greater than the value prior to it, but decided to use try this approach instead, lol.

def check_binary_search_tree_(root):
    # node, min val in current range, max val in current range. Range updates every time a new node is visited. Given the range values, I can implicitly tell whether I'm moving either to the left or to the right.
    stack = [(root, 0, 10e4)]

    while stack:
        current, min_in_range, max_in_range = stack.pop()
        if not (min_in_range < current.data < max_in_range):
            return False

        if current.right:
            stack.append((current.right, current.data, max_in_range))
        if current.left:
            stack.append((current.left, min_in_range, current.data))

    return True