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

Intermediate

Apr 2026

Summary

Amazon SWE online assessment with a greedy/counting problem about dispatching warehouse items in minimum actions. Pretty standard OA format, nothing too wild.

Questions Asked (1)

Given an array representing the zones of m items in a warehouse, find the minimum number of dispatch actions needed to ship all items, where you can either send two items from different zones together or send one item alone.

Algorithms & Data Structures

Author's notes

The key insight is figuring out how often the most frequent zone forces you into single dispatches.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem: we need to pair items from different zones to minimize total dispatches, with each dispatch being either a pair from different zones or a single item. Then, recognize that the optimal strategy is to pair as many items from different zones as possible, which reduces to a greedy approach based on the most frequent zone.

Pro tip: After deriving the formula, explicitly discuss edge cases like when one zone has more than half the items, and mention that the solution runs in O(n) time and O(1) space if we only track the maximum frequency.

1. Clarify the problem

Restate the problem in your own words and ask clarifying questions about constraints, input format, and whether items within the same zone can be paired.

2. Identify the key constraint

Note that pairs must be from different zones, so the limiting factor is the zone with the most items. If that zone has more than half the total items, some items from that zone must be sent alone.

3. Derive the formula

Let n be the total number of items and m be the maximum frequency of any zone. The minimum number of dispatches is max(m, ceil(n/2)). Explain why: each dispatch can cover at most 2 items, and items from the same zone cannot be paired together.

4. Validate with examples

Test the formula with small examples, such as all items in one zone (answer n), two zones with equal counts (answer n/2), and one dominant zone (answer m).

5. Analyze complexity

State that the algorithm requires counting frequencies, which can be done in O(n) time and O(k) space where k is the number of zones, or O(1) if we only track the maximum frequency.

Key Points to Mention

The problem reduces to pairing items from different zones, which is equivalent to the 'task scheduler' or 'reorganize string' pattern.
The minimum number of dispatches is max(max_frequency, ceil(total_items / 2)).
Greedy pairing works: always pair the most frequent zone with another zone.
Edge cases: all items in one zone, two zones with equal counts, and one zone with more than half the items.
Time complexity O(n) and space complexity O(1) if only the maximum frequency is tracked.
Connection to real-world warehouse optimization: minimizing dispatch actions reduces shipping costs.

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