# Creates a nested dictionary indexed by level and
# radius as coordinates pointing to each node.info
def tree_Coords(root, d, radius, level):
    if not root:
        return
    if level not in d.keys():
        d[level] = dict()
    d[level].update({radius: root.info})
    tree_Coords(root.left, d, radius-1, level+1)
    tree_Coords(root.right, d, radius+1, level+1)

def topView(root):
    radius = 0
    level = 0
    if not root:
        return
    d = dict()
    tree_Coords(root, d, radius, level)
    res = dict()
    
    # Nested loop scans and adds values to res when no value exists for
    # a specific radius. If raidus index already exists in res, then there existed
    # another value with the same radius on a previous level(above).
    for level in d.keys():
        for radius in d[level].keys():
            if radius not in res.keys():
                res[radius] = d[level][radius]

    for r in sorted(res.keys()):
        print(res[r], end=" ")