def topView(root):
Q=deque([])
top_view={}

Q.append((root,0))
while Q:
    node,h = Q.popleft()
    if not node:
        continue
    if h not in top_view:
        top_view[h]=node
    Q.append((node.left,h-1))
    Q.append((node.right,h+1))

for some reason they don't let me post the bottom half, anyway sort top_view by key and print the values