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Amazon·Software Engineer·Online Assessment (OA)·Junior

Junior
May 2026

Summary

Amazon SDE internship OA with a tricky algorithmic problem about distributing data across two regions while maximizing affinity scores under some pairing constraints. The problem looked approachable at first glance but the rule pairs add a layer that trips you up if you're not careful.

Questions Asked (1)

Q1

You have n data pieces (n is even), each with an affinity value. You need to distribute them between two regions by alternating selections, where each region greedily picks to maximize its total affinity. There are also m pairing rules: if one piece from a pair is picked for a region, the other must go to the next region in the following step. Find the maximum possible affinity sum for RegionA.

Algorithms & Data Structures
Author's notes

This one messed me up more than I expected.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem constraints and the greedy alternating selection process, including how pairing rules affect choices. Then, model the game as a turn-based selection with dependencies and propose an algorithm (e.g., dynamic programming with bitmask for small n, or greedy with priority queues for large n) to compute the maximum affinity for RegionA. Finally, analyze time and space complexity and discuss potential optimizations.

Pro tip: Emphasize that the greedy choice of each region may not lead to a globally optimal outcome for RegionA, so you need to consider strategic play or lookahead. Mention that pairing rules can be represented as a graph and may require topological ordering or union-find to handle constraints efficiently.

1. Clarify the problem

Restate the problem in your own words, confirming the rules: alternating picks, greedy selection by each region, and the effect of pairing rules. Ask clarifying questions about edge cases, such as whether a region can skip a turn if no valid pick exists.

2. Model the game

Represent the data pieces and pairing rules as a graph or set of constraints. Identify that the greedy choice of each region depends on the current available pieces and the forced moves from previous picks.

3. Design an algorithm

Propose an approach: for small n, use minimax with memoization or DP over subsets; for large n, consider greedy with priority queues and handle forced moves via a queue. Discuss how to incorporate pairing rules, possibly using union-find to track connected components.

4. Analyze complexity

State the time and space complexity of your proposed solution. For DP, it's O(2^n * n); for greedy, it's O(n log n + m). Discuss trade-offs and scalability.

5. Test and validate

Walk through a small example to verify the algorithm, checking that pairing rules are respected and that RegionA's sum is maximized. Consider edge cases like all affinities equal or pairing rules forming cycles.

Key Points to Mention

  • Greedy vs. optimal: each region's greedy choice may not maximize RegionA's total, so consider strategic play.
  • Pairing rules as constraints: model as a graph, use union-find or topological sort to handle forced moves.
  • Dynamic programming with bitmask for small n, or greedy with priority queues for large n.
  • Time and space complexity analysis and trade-offs.
  • Edge cases: cycles in pairing rules, equal affinities, and forced moves that skip a turn.
  • Communication: clarify assumptions and walk through examples.

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