How should I practice Unique One-Region Sizes in a Binary Tree?

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

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

Unique One-Region Sizes in a Binary Tree

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Problem statement

You are given a binary tree whose node values are only 0 or 1. A one-region is a maximal connected component of value-1 nodes using parent-child edges.

Return the distinct region sizes in increasing order. Return an empty array for an empty tree or a tree with no value-1 nodes.

Function

uniqueOneRegionSizes(root: TreeNode) → int[]

Examples

Example 1

root = [1,1,0,1,0,1,1]return = [1,3]

The left connected region has size 3; the two right children form one size-2 region? In level order they share a zero parent, so they are separate size-1 regions, producing sizes 1 and 3.

Example 2

root = [0,0,0]return = []

No node has value 1.

Example 3

root = []return = []

An empty tree has no regions.

Constraints

The tree has at most 2000 nodes.
Every node value is 0 or 1.