Microsoft·Machine Learning Engineer·Technical Phone Screen·Intermediate

Intermediate

Jun 2026

Summary

Microsoft ML Engineer interview with an array problem that looks simple but has a few edge cases worth thinking through carefully. Nothing too wild, just clean problem solving.

Questions Asked (1)

Given an unsorted integer array, find the minimum absolute difference between any two distinct elements, then return all pairs that achieve that minimum difference. Each pair should be ordered smallest to largest, and the list of pairs should be sorted ascending by first element.

Algorithms & Data Structures

Author's notes

My first instinct was brute force, compare every pair, O(n^2).

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AI HintsAI Generated

Suggested Approach

Start by sorting the array, then perform a single pass to compute differences between adjacent elements, tracking the minimum difference and collecting all pairs that achieve it. This yields O(n log n) time and O(n) space for the output, which is optimal for comparison-based sorting.

Pro tip: Mention that sorting is the key insight because the minimum absolute difference must occur between adjacent elements in sorted order, and discuss how to handle duplicates (difference 0) and edge cases like arrays with fewer than two elements.

1. Clarify and Validate Input

Confirm the array size, element range, and whether duplicates are allowed. Handle edge cases: if the array has fewer than 2 elements, return an empty list.

2. Sort the Array

Sort the array in ascending order. This ensures that any pair with the minimum absolute difference will be adjacent in the sorted order.

3. Single Pass to Find Minimum Difference and Collect Pairs

Iterate through the sorted array, compute the difference between each adjacent pair, and track the minimum difference. Collect all pairs that achieve this minimum, ensuring each pair is ordered smallest to largest.

4. Sort and Return the Result

Since the array is sorted, the collected pairs will naturally be in ascending order by first element. Return the list of pairs.

Key Points to Mention

Time complexity: O(n log n) due to sorting, which is optimal for comparison-based approaches.
Space complexity: O(n) for the output list, but O(1) extra space if we ignore the output and sorting is in-place.
Proof that minimum difference occurs between adjacent elements in sorted order.
Handling duplicates: if duplicates exist, the minimum difference is 0 and all duplicate pairs should be returned.
Edge cases: empty array, single element, all elements identical.
Alternative approaches: brute-force O(n^2) is inefficient; sorting is preferred.

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