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Interactive·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
May 2026

Summary

Technical phone screen for a Data Engineer role at Interactive. One coding question, scheduling/simulation style, and they wanted an O(n) solution which I was not fully prepared for.

Questions Asked (1)

Q1

Given a list of products to produce in order and a cooling period that prevents producing the same product type back-to-back within a certain number of days, write a function to find the minimum number of days to produce all products.

Algorithms & Data Structures
Author's notes

My first instinct was simulation, just track the last day each product type was produced and advance a day counter accordingly.

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AI HintsAI Generated

Suggested Approach

Model the problem as a task scheduling problem with cooldown constraints. Use a greedy approach with a max-heap to always produce the most frequent remaining product, and a queue to track products in cooldown. Simulate day by day, incrementing the day count until all products are produced.

Pro tip: Clarify whether the cooling period applies to consecutive productions of the same product or any same product within the period. Also, discuss edge cases like empty list or cooling period 0, and mention that the greedy approach is optimal for this problem.

1. Understand the problem and constraints

Restate the problem: given a list of product types and a cooling period n, find the minimum days to produce all products without producing the same type within n days. Clarify input/output and edge cases.

2. Choose the right data structures

Use a frequency map to count occurrences of each product. Use a max-heap to efficiently retrieve the most frequent available product, and a queue to manage products in cooldown with their remaining cooldown days.

3. Simulate the production process

Iterate day by day. Each day, if the heap is not empty, pop the most frequent product, decrement its count, and if still >0, add it to the cooldown queue with cooldown n. Also, check the queue for any product whose cooldown expires today and push it back to the heap.

4. Handle idle days and termination

If the heap is empty but the queue is not, it means we must idle. Increment the day count and continue. Stop when both heap and queue are empty. Return the total days.

5. Analyze complexity and test

Discuss time complexity O(total tasks * log k) where k is number of unique products, and space O(k). Walk through a small example to verify correctness.

Key Points to Mention

  • Greedy strategy: always produce the most frequent available product to minimize idle days.
  • Use of max-heap (priority queue) for efficient retrieval of most frequent product.
  • Use of queue to track products in cooldown and their remaining cooldown days.
  • Simulation day by day, handling idle days when no product is available.
  • Time and space complexity analysis.
  • Edge cases: empty input, cooling period 0, all products same, etc.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.