Microsoft·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Microsoft SWE coding round, one question the whole time. Pretty focused on in-place array manipulation which I don't practice enough.

Questions Asked (1)

Given an unsorted array of integers, remove duplicates in-place and return the deduplicated array. You cannot use any additional data structures.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The no-extra-data-structure constraint is what makes this annoying.

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AI HintsAI Generated

Suggested Approach

Clarify the problem constraints and edge cases first, then propose an in-place algorithm using two pointers to overwrite duplicates. Explain the time and space complexity, and discuss trade-offs compared to using extra space.

Pro tip: Mention that while the problem forbids additional data structures, you can still achieve O(n) time by sorting the array in-place first (if allowed) or by using a two-pointer technique that doesn't require extra space. Also, discuss how the solution would differ if the array were sorted.

1. Clarify requirements and constraints

Ask whether the array can be modified, whether the order of elements matters, and what the expected return type is (e.g., new length or the array itself). Confirm that no additional data structures (like hash sets) are allowed.

2. Consider approaches and trade-offs

Discuss possible strategies: sorting first (O(n log n) time, O(1) space) then removing duplicates, or using a two-pointer technique for unsorted arrays (O(n^2) time, O(1) space). Highlight the trade-off between time and space.

3. Design the algorithm

For the chosen approach, outline the steps: e.g., for two-pointer, iterate with a write pointer and a read pointer, comparing each element to the last unique element and overwriting duplicates.

4. Analyze complexity and edge cases

State the time and space complexity of your solution. Discuss edge cases: empty array, single element, all duplicates, no duplicates, and large arrays.

5. Test with examples

Walk through a small example (e.g., [1,2,2,3,1]) to demonstrate how the algorithm works step by step, ensuring correctness.

Key Points to Mention

In-place modification means O(1) extra space, so no hash sets or auxiliary arrays.
Two-pointer technique: one pointer for the next unique position, another to scan the array.
Time complexity: O(n^2) for unsorted two-pointer, O(n log n) if sorting is allowed.
Space complexity: O(1) additional space.
Edge cases: empty array, single element, all elements identical.
Trade-offs: sorting changes order but may be acceptable if order isn't required; two-pointer preserves order but is slower.

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