def rightSideView(root):
res = []
q = collections.deque()
if root:
q.append(root)
while q:
rightSide = None
for i in range(len(q)):
node = q.popleft()
if node:
rightSide = node
q.append(node.left)
q.append(node.right)
if rightSide:
res.append(rightSide.val)
return res