Find root IDs and paths
Company: ZipHQ
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: Medium
Interview Round: Technical Screen
You are given a collection of string blocks, each represented as a JSON object with fields {"id": string, "parentId": string | null}. A block is a root if it has no parent (parentId is null or the referenced parent does not appear).
1) Write a function that returns all root ids from the input.
2) Follow-up: given a target id, return the path of ids from its root to that id. Explain your approach, the data structures you use, and analyze time and space complexity.
Quick Answer: This question evaluates understanding of graph/tree relationships, identification of root nodes, and path reconstruction from parent references, assessing algorithmic reasoning and data-structure familiarity.