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

Intermediate
Jun 2026

Summary

Amazon SWE online assessment with an interval merging problem that looks straightforward but has a few edge cases that'll trip you up if you're not careful.

Questions Asked (1)

Q1

Given a list of delivery zones represented as intervals, and a maximum length k, add exactly one new interval of length at most k to minimize the number of disconnected groups (connected components) in the resulting set of intervals.

Algorithms & Data Structures
Author's notes

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AI HintsAI Generated

Suggested Approach

First, sort the intervals and compute the initial number of connected components. Then, identify gaps between consecutive components and determine which gaps can be bridged by a single interval of length at most k, prioritizing the largest gaps to maximize the reduction in components. Finally, return the minimum number of components after adding the interval.

Pro tip: Clarify whether the new interval must be placed entirely within existing gaps or can overlap with existing intervals; this affects the bridging condition. Also, consider edge cases like no intervals or k=0.

1. Sort and Merge Intervals

Sort the intervals by start time and merge overlapping or adjacent intervals to identify the initial connected components.

2. Identify Gaps Between Components

For each pair of consecutive components, compute the gap length as the distance between the end of the first and the start of the second.

3. Determine Bridgeable Gaps

A gap can be bridged by a new interval of length at most k if the gap length is less than or equal to k. The new interval can be placed to cover the gap and connect the two components.

4. Maximize Reduction in Components

Bridging a gap reduces the number of components by 1. To minimize the final number of components, choose the largest bridgeable gap (or any if multiple) to bridge, as each bridge reduces components by exactly 1.

5. Compute Final Components

The minimum number of components is the initial number of components minus 1 if there is at least one bridgeable gap; otherwise, it remains the same.

Key Points to Mention

  • Sorting intervals by start time to efficiently find gaps.
  • Merging overlapping intervals to compute initial connected components.
  • Gap length calculation: gap = next.start - current.end.
  • Condition for bridging: gap <= k.
  • Each bridge reduces the number of components by exactly 1.
  • Edge cases: no intervals, single interval, k=0, gaps larger than k.

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