"""
This is a very common interview question. 
Given a binary tree, check whether it’s a binary 
search tree or not. Simple as that.. 
http://www.ardendertat.com/2011/10/10/programming-interview-questions-7-binary-search-tree-check/
"""


"""
This is a very common interview question. 
Given a binary tree, check whether it’s a binary 
search tree or not. Simple as that.. 
http://www.ardendertat.com/2011/10/10/programming-interview-questions-7-binary-search-tree-check/
"""

class Node:
    def __init__(self, val=None):
        self.left, self.right, self.val = None, None, val
add node