isitsearchtree

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

def check_binary_search_tree_(root, values = None, leftParent = None, rightParent = None, parent = None):
    #print root.data
    #print root.left
    #print root.right
    toReturn = True

    if values == None:
        values = dict()
        leftParent = root
        rightParent = root
        parent = root
    '''
    print root.data
    if root.right:
        print root.right.data
    if root.left:
        print root.left.data
    print "left par = " + str(leftParent.data)
    print "right par = " + str(rightParent.data)
    print "-------------"
    '''

    if not root.data in values:
        values[root.data] = True
    else:
        return False

    #print values
    if (root.left):
        if (root.left.data > root.data):
            return False
        elif(root == leftParent):
            toReturn = check_binary_search_tree_(root.left, values, leftParent = root.left, rightParent = root, parent = root)
        elif(root.left.data > leftParent.data):
            toReturn = check_binary_search_tree_(root.left, values, leftParent = leftParent, rightParent = root, parent = root)
        else:
            return False

    if (root.right and toReturn):
        if (root.right.data < root.data):
            return False
        elif (root == rightParent):
            toReturn = check_binary_search_tree_(root.right, values, leftParent = root, rightParent = root.right, parent = root)
        elif (root.right.data < rightParent.data):
            toReturn = check_binary_search_tree_(root.right, values, leftParent = root, rightParent = rightParent, parent = root)
        else:
            return False

    return toReturn