def top_view(root):

if root is not None:

dict = {}

node_dict = {}

que = list()

que.append(root)

node_dict[root.data] = 0

while len(que) > 0:

temp = []

curr = que.pop(0)

if curr is not None:

level = node_dict[curr.data]

if level not in dict:

temp.append(curr.data)

dict[level] = temp

if curr.left is not None:

left_node = curr.left

que.append(left_node)

node_dict[left_node.data] = node_dict[curr.data] - 1

if curr.right is not None:

right_node = curr.right

que.append(right_node)

node_dict[right_node.data] = node_dict[curr.data] + 1

print(dict)