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Amazon·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Amazon SWE coding round, 40 minutes, one problem involving a circular array with multiple distance queries. Pretty focused session, no fluff.

Questions Asked (1)

Q1

Given a circular array of distances and multiple query segments, compute the total minimum distance across all queries.

Algorithms & Data Structures
Author's notes

Looks like a bus stop shortest path problem at first glance but the multi-query angle changes things.

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AI HintsAI Generated

Suggested Approach

Clarify the problem: a circular array of distances between adjacent points, and queries asking for the minimum distance between two points along the circle. Precompute prefix sums of the linear array to answer each query in O(1) by comparing the clockwise distance and its complement. Sum the minimum distances across all queries.

Pro tip: Mention that the minimum distance is min(clockwise, total - clockwise), and handle edge cases like when the start index is greater than the end index by swapping or adjusting. Also, discuss potential follow-ups like multiple queries or dynamic updates.

1. Clarify the problem

Confirm that the circular array represents distances between consecutive points, and each query asks for the shortest path between two points along the circle. Ask about input format, constraints, and whether queries are independent.

2. Preprocess for O(1) queries

Compute prefix sums of the linear distances to quickly calculate the clockwise distance between any two indices. Also compute the total circumference.

3. Answer each query

For a query (i, j), ensure i <= j by swapping if needed. Compute clockwise distance as prefix[j] - prefix[i]. The minimum distance is min(clockwise, total - clockwise).

4. Sum and return

Accumulate the minimum distances for all queries and return the total sum. Discuss time complexity: O(n) preprocessing, O(1) per query, O(q) total.

Key Points to Mention

  • Prefix sums for O(1) range sum queries
  • Total circumference as sum of all distances
  • Minimum of clockwise and counterclockwise distances
  • Handling indices when start > end (swap or adjust)
  • Time and space complexity analysis
  • Edge cases: same point, adjacent points, full circle

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