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Amazon·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Amazon SWE coding round, two questions back to back, both from the classic scheduling/interval problem family. Nothing too exotic but you need to actually know your data structures cold.

Questions Asked (2)

Q1

Given a list of meeting time intervals, determine whether a person can attend all meetings without any overlap.

Algorithms & Data Structures
Author's notes

Sort by start time and check adjacent pairs.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem: intervals are inclusive/exclusive, input format, and edge cases. Then propose sorting intervals by start time and checking for overlaps between consecutive intervals. Analyze time and space complexity, and discuss potential optimizations or alternative approaches.

Pro tip: Mention that sorting is key, but also consider if the input is already sorted or if we can use a sweep line approach for streaming data. This shows you think about scalability and real-world scenarios.

1. Clarify requirements and edge cases

Ask about interval inclusivity, input format, and constraints. Discuss edge cases like empty list, single meeting, and back-to-back meetings.

2. Propose sorting-based approach

Sort intervals by start time. Then iterate through the sorted list, checking if the current meeting's start time is less than the previous meeting's end time.

3. Analyze complexity

State that sorting takes O(n log n) time, and the linear scan takes O(n) time, resulting in O(n log n) overall. Space complexity is O(1) if sorting in-place, or O(n) if creating a new list.

4. Discuss alternative approaches

Mention that if intervals are already sorted, we can do it in O(n). Also, for streaming data, a min-heap or sweep line could be used, but sorting is simplest for static input.

5. Write pseudocode or code

If asked, write clean code with clear variable names, handling edge cases, and possibly test with examples.

Key Points to Mention

  • Sorting intervals by start time
  • Checking overlap condition: current.start < previous.end
  • Time complexity: O(n log n) due to sorting
  • Space complexity: O(1) or O(n) depending on sorting implementation
  • Edge cases: empty input, single interval, back-to-back meetings
  • Alternative: sweep line or heap for streaming data

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

Q2

Given a list of meeting time intervals, find the minimum number of conference rooms required to hold all meetings.

Algorithms & Data Structures
Author's notes

This one took me a minute.

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AI HintsAI Generated

Suggested Approach

Clarify the problem and constraints, then discuss the two main approaches: sorting start and end times separately with a two-pointer technique, or using a min-heap to track end times. Analyze time and space complexity for each, and choose the one that best fits the constraints and is easiest to implement correctly.

Pro tip: Mention that the problem is equivalent to finding the maximum number of overlapping intervals at any point, and that the heap approach naturally extends to scheduling problems with room assignments. Also, proactively discuss edge cases like empty input and back-to-back meetings.

1. Clarify and Restate

Ask clarifying questions about input format, interval inclusivity, and constraints. Restate the problem to ensure understanding.

2. Discuss Approaches

Explain the two common approaches: sorting start and end times separately with two pointers, and using a min-heap to track end times. Compare their time and space complexities.

3. Choose and Implement

Select the approach that is most efficient and easiest to implement. Walk through the code or pseudocode step by step.

4. Test with Examples

Run through provided examples and edge cases (e.g., empty list, single meeting, all overlapping) to verify correctness.

5. Analyze Complexity

State the time and space complexity of the chosen solution and discuss potential optimizations or trade-offs.

Key Points to Mention

  • The problem reduces to finding the maximum number of overlapping intervals at any time.
  • Sorting start and end times separately allows a two-pointer sweep to count active meetings.
  • A min-heap can efficiently track the earliest ending meeting to reuse rooms.
  • Time complexity: O(n log n) due to sorting; space complexity: O(n) for the heap or sorted arrays.
  • Edge cases: empty input, meetings that end exactly when another starts (non-overlapping), and all meetings overlapping.
  • The heap approach can be extended to assign specific rooms if needed.

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