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

Intermediate

Apr 2026

Summary

Round 4 at Microsoft for a software engineering role. Just one coding question, interval merging variant, nothing too exotic but you need to have the pattern down cold.

Questions Asked (1)

Given a list of intervals, output all overlapping intervals (a variant of the classic merge intervals problem).

Algorithms & Data Structures

Author's notes

Sort first, then scan and track where intervals overlap.

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AI HintsAI Generated

Suggested Approach

First clarify whether 'overlapping intervals' means merging all overlapping intervals into disjoint ranges or listing every pair that overlaps. Then present a solution: sort intervals by start time, iterate while tracking the current merged interval, and output merged intervals when a gap is found. If listing pairs, use a sweep line or interval tree approach.

Pro tip: Microsoft interviewers value clean, bug-free code and clear communication. Before coding, state your assumptions and walk through a small example to confirm the expected output format.

1. Clarify the problem

Ask whether the output should be merged intervals or all overlapping pairs, and whether intervals are closed or half-open. Confirm input format and edge cases.

2. Choose the right algorithm

For merging: sort by start time and use a single pass. For listing pairs: consider sweep line or interval tree. Explain time/space complexity.

3. Walk through an example

Trace the algorithm on a small example like [[1,3],[2,6],[8,10],[15,18]] to verify correctness and output format.

4. Implement and test

Write clean code with meaningful variable names. Test edge cases: empty list, single interval, touching intervals, nested intervals.

5. Analyze and optimize

State time complexity (O(n log n) due to sorting) and space complexity (O(n) for output). Discuss potential optimizations if needed.

Key Points to Mention

Sorting intervals by start time is key to simplifying the problem.
Merge condition: if current interval's start <= last merged interval's end, they overlap.
Edge cases: empty input, single interval, intervals that just touch (e.g., [1,2] and [2,3]).
Time complexity: O(n log n) for sorting, O(n) for merging; space O(n) for output.
If asked for all overlapping pairs, a sweep line with active intervals can be used.
Communication: explain your thought process and confirm assumptions before coding.

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