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Microsoft·Software Engineer·Onsite - Coding / Algorithms·Intermediate

Intermediate
May 2026

Summary

Microsoft SWE coding round, one algorithm question about finding pairs in an array. Pretty standard fare but the edge cases are where it gets interesting.

Questions Asked (1)

Q1

Given an array of integers, find all pairs that have the minimum absolute difference between them.

Algorithms & Data Structures
Author's notes

I started sorting the array which was the right call, but then I fumbled around trying to explain why for like a minute.

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AI HintsAI Generated

Suggested Approach

Start by sorting the array, then traverse it once to find the minimum absolute difference between adjacent elements. After identifying the minimum difference, collect all adjacent pairs that have that difference.

Pro tip: Mention that sorting is optimal for this problem because the minimum difference must occur between adjacent elements in sorted order, and discuss the trade-off between time and space complexity.

1. Clarify and Confirm

Ask if the array can contain duplicates, if the order of pairs matters, and if the output should be sorted. Confirm the expected time and space complexity.

2. Sort the Array

Sort the array in ascending order. This ensures that the minimum absolute difference will be between adjacent elements.

3. Find Minimum Difference

Iterate through the sorted array and compute the absolute difference between each pair of adjacent elements. Keep track of the minimum difference found.

4. Collect All Pairs

Perform a second pass (or combine with step 3) to collect all adjacent pairs whose absolute difference equals the minimum difference.

5. Return the Result

Return the list of pairs. If required, sort the pairs or the result list according to the problem's specification.

Key Points to Mention

  • Time complexity: O(n log n) due to sorting, and O(n) for the linear scans.
  • Space complexity: O(1) extra space if we ignore the output, or O(n) if considering the output list.
  • Sorting ensures that the minimum difference is between adjacent elements, which is a key insight.
  • Edge cases: empty array, single element, all elements equal, negative numbers.
  • Handling duplicates: if duplicates exist, the minimum difference is 0, and all duplicate pairs should be included.
  • Alternative approaches: brute force O(n^2) is inefficient; sorting is optimal.

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