Katkat
Back

Design a data structure for dynamic top‑K frequency

BloombergSoftware Engineer · Technical Screen
HardSoftware EngineerTechnical ScreenCoding & Algorithms

Last updated

This question evaluates data structure and algorithm design skills, focusing on frequency counting, dynamic maintenance of top-K elements, and efficient update and query operations in a multiset within the Coding & Algorithms domain.

Design a data structure that maintains a multiset of integers and supports the following operations efficiently:

Operations

  • insert(x): Add one occurrence of value x.
  • remove(x): Remove one occurrence of value x if it exists (if x is not present, do nothing).
  • topK(k) -> List[int]: Return the k most frequent values currently in the multiset.

Requirements / Clarifications

  • Frequency means the current count of each value in the multiset.
  • If fewer than k distinct values exist, return all distinct values.
  • If multiple values have the same frequency, you may return them in any order (or state and implement a deterministic tie-break such as smaller value first).
  • Discuss time and space complexity for each operation.
  • Explain why your chosen data structures are appropriate compared with alternatives (e.g., sorting on every query, balanced BST/TreeMap, etc.).
  • Consider edge cases (removing down to zero, repeated inserts/removes, large k, empty structure).
  • Bonus discussion: how would your approach change if the number of total updates is extremely large (e.g., up to billions)?