How do you find the k-th largest element in an array?

0-2 years experience

1. 1Given an unsorted array of ten integers, write a function that returns the 3rd largest element. How would you approach it?
2. 2If you decide to sort the array first, what are the time and space complexities for finding the k‑th largest?
3. 3What should your function return or do when k is larger than the array length?

2-5 years experience

1. 1Our service must return the k‑th largest transaction amount from a list that can contain up to one million entries. Which algorithm would you choose and why?
2. 2We implemented quickselect but observed occasional timeouts on certain inputs. How would you modify the implementation to avoid those worst‑case scenarios?
3. 3A teammate used a min‑heap of size k, but memory usage spikes under load. What could be causing that and how would you fix it?

5-8 years experience

1. 1Design a component that continuously receives a high‑velocity stream of numbers and must be able to query the k‑th largest at any time. Discuss data structures, concurrency, and scaling considerations.
2. 2Our analytics pipeline stores billions of values across distributed nodes. How would you compute the global k‑th largest efficiently?
3. 3If the dataset resides on disk and cannot fit into memory, what strategy would you use to find the k‑th largest element?

8+ years experience

1. 1We are migrating a legacy reporting system that currently sorts entire datasets to compute top‑k metrics. How would you redesign the architecture to support real‑time k‑th largest queries across multiple services?
2. 2Across several teams we need a shared library for top‑k selection that works with different data types and can be extended. What design principles would you enforce to ensure performance, correctness, and maintainability?
3. 3At petabyte scale, would you build a custom quickselect service or rely on a distributed processing framework for k‑th largest calculations? Explain the trade‑offs.