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Compute task order with prerequisites

SnowflakeSoftware Engineer · Technical Screen
MediumSoftware EngineerTechnical ScreenCoding & Algorithms

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This question evaluates proficiency in graph algorithms—particularly topological ordering and cycle detection—along with the use of efficient data structures for representing dependencies and analyzing time and space complexity.

Given an integer n representing tasks labeled 0..n-1 and a list of prerequisite pairs (a, b) meaning b must be completed before a, return any valid ordering of tasks that completes all tasks, or an empty list if no ordering exists. Design an efficient algorithm and data structures, explain how you detect cycles, and analyze time and space complexity. Follow-ups: (

  1. How would you produce all tasks that are part of at least one cycle? (
  2. How would you handle up to 100,000 tasks and 200,000 prerequisites?