cousin python

# http://code2begin.blogspot.com
# program to print if 2 nodes of a binary tree are cousins or not

# node class
class node:
    def __init__(self, element):
        self.data = element
        self.left = None
        self.right = None


# function to find and return the level of a node in binary tree
def level_of_node(root, data, level=-1):
    # if the tree is empty or if we reach a leaf node then return 0
    if root is None:
        return -1
    if root.data == data:
        return level + 1

    # check in the left subtree for the element
    # if found then return the level
    level_node = level_of_node(root.left, data, level + 1)
    if level_node != -1:
        return level_node

    # searching for the node in right subtree
    level_node = level_of_node(root.right, data, level + 1)
    return level_node



# function to check if 2 nodes are siblings or not
def isSibling(parent, n1, n2):
    if parent is None:
        return False

    if parent.left is not None and parent.right is not None:
        return (parent.left.data == n1 and parent.right.data == n2) or (parent.left.data == n2 and parent.right.data == n1)

    return isSibling(parent.left, n1, n2) or isSibling(parent.right, n1, n2)


def isCousin(root, a, b):
    if (level_of_node(root, a) == level_of_node(root, b)) and isSibling(root, a, b):
        return True
    return False


head = node(1)
head.left = node(2)
head.right = node(3)
head.left.left = node(4)
head.left.right = node(5)
head.right.right = node(6)
head.left.left.right = node(7)
head.right.right.left = node(8)
head.left.left.right.left = node(9)
head.left.left.right.left.left = node(10)
head.right.right.left.right = node(11)
print("Nodes 2 and 3 are siblings : " + str(isCousin(head, 2, 3)))
print("Nodes 6 and 10 are siblings : " + str(isCousin(head, 6, 10)))
print("Nodes 7 and 8 are siblings : " + str(isCousin(head, 7, 8)))