import collections

def zigzag_level_order_traversal(root):
    if root is None:
        return []

    result = []
    q = collections.deque([root]) #insert the first node

    rtol = False
    while len(q) != 0:

        numnodes = len(q) # get the number of nodes in deque
        temp = []

        for _ in range(numnodes):

            node = q.popleft() # store the first val of the deque in node
            temp.append(node.label) #append to the temp for that level

            if node.left_ptr is not None:
                q.append(node.left_ptr)

            if node.right_ptr is not None:
                q.append(node.right_ptr)

        if rtol is True:
            temp.reverse()
        rtol = not rtol

        result.append(temp)

    return (result)