Tree Traversal Target: 15s
BFS level-by-level. Take the last node of each level. Standard level-order with level_size tracking.
from collections import deque
def rightSideView(root):
if not root: return []
res = []
q = deque([root])
while q:
level_size = len(q)
for i in range(level_size):
node = q.popleft()
if i == level_size - 1:
res.append(node.val) # rightmost in level
if node.left: q.append(node.left)
if node.right: q.append(node.right)
return resType it from memory. Go.