TreesTrees: Is This a Binary Search Tree?

""" Node is defined as
class node:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None
"""
def checknode(node,min,max):
    if node == None:
        return True
    #print(node.data,min,max) min max被传递下去
    if node.data<=min or node.data>=max:
        return False
    return checknode(node.left,min,node.data) and checknode(node.right,node.data,max)


def checkBST(root):
    return checknode(root,float('-inf'),float('inf'))