How should I practice Boundary of Binary Tree?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Bloomberg LP phone screen problems in FastPrep.

Is Boundary of Binary Tree associated with Bloomberg LP?

FastPrep tags this as a Bloomberg LP phone screen coding practice problem when the problem catalog has that company and stage context.

Boundary of Binary Tree

Bloomberg LP● MediumNEW GRADPHONE SCREEN

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Problem statement

Given a binary tree, return its anti-clockwise boundary: the root, the left boundary excluding leaves, every leaf from left to right, and the right boundary excluding leaves in bottom-up order.

Do not include any node more than once.

Function

boundaryOfBinaryTree(root: TreeNode) → int[]

Examples

Example 1

root = [1,null,2,3,4]return = [1,3,4,2]

Three and four are leaves, and two closes the right boundary.

Example 2

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

The boundary walks around the complete tree without duplicates.

Constraints

The tree contains between 0 and 10^5 nodes.
-10^9 <= Node.val <= 10^9.