def inorder_list(root):
    values = []
    def inorder_t(root):
        if root is None:
            return
        inorder_t(root.left)
        values.append(root.data)
        inorder_t(root.right)
    inorder_t(root)
    return values

def check_binary_search_tree_(root):
    if root is None:
        return
    values = inorder_list(root)
    if values == sorted(values) and len(values) == len(set(values)):
        return True
    else:
        return False