Left View / Right View of Binary Tree

Given the root of a binary tree, return both the **left view** and **right view**.

- **Left view**: The first node visible when looking from the left side at each level.

- **Right view**: The last node visible when looking from the right side at each level.

Input: root = [1,2,3,4,5,6,7]

Output: { left: [1,2,4], right: [1,3,7] }

First and last node of each level.

Input: root = [1,2,null,3]

Output: { left: [1,2,3], right: [1,2,3] }

Only one node per level.

Time

O(n)

BFS visits all nodes.

Space

O(n)

queue storage.

#1 Full tree

Input: [1,2,3,4,5,6,7]

Expected: {"left":[1,2,4],"right":[1,3,7]}

#2 Left-skewed

Input: [1,2,null,3]

Expected: {"left":[1,2,3],"right":[1,2,3]}

#3 Empty tree

Input: []

Expected: {"left":[],"right":[]}