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

IntermediatePrefer not to say
May 2026

Summary

Microsoft SWE round that mixed behavioral and coding in the same session. The coding problem was LFU cache, which is one of those problems that looks manageable until you try to get everything to O(1) and realize you need two separate maps plus a linked list per frequency bucket.

Questions Asked (2)

Q1

Walk through a situation where you had significant impact, resolved a conflict, or had to prioritize competing work.

Conflict ResolutionRoadmap Prioritization
Author's notes

Standard behavioral stuff, nothing unexpected.

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AI HintsAI Generated

Suggested Approach

Choose a single, specific situation where you had a measurable impact, resolved a conflict, or prioritized competing work, and narrate it using the STAR method. Focus on your individual actions, the trade-offs you made, and the quantifiable outcome, while showing alignment with Microsoft's culture of collaboration and customer obsession.

Pro tip: Quantify your impact with metrics (e.g., latency reduction, revenue increase, time saved) and explicitly tie your decisions to Microsoft's values like 'One Microsoft' or 'Customer Obsessed' to show cultural fit.

1. Set the Context

Briefly describe the project, team, and stakes so the interviewer understands the situation. Mention the competing priorities or conflict without diving into unnecessary details.

2. Define the Challenge

Clearly state the conflict, competing work, or impact opportunity and why it was difficult. Highlight the constraints (time, resources, differing opinions) to show complexity.

3. Describe Your Actions

Explain the specific steps you took to resolve the conflict, prioritize work, or drive impact. Emphasize your thought process, collaboration, and any trade-off decisions.

4. Highlight the Outcome

Share the measurable results of your actions, such as improved performance, resolved disagreement, or delivered features. Use metrics to quantify impact.

5. Reflect and Learn

Conclude with what you learned and how it changed your approach, showing growth and self-awareness.

Key Points to Mention

  • Specific metrics or data points that quantify the impact (e.g., reduced latency by 30%, increased user engagement by 15%)
  • Trade-off analysis: how you evaluated competing priorities and made a decision (e.g., using impact/effort matrix, consulting stakeholders)
  • Conflict resolution approach: active listening, finding common ground, and aligning on shared goals
  • Collaboration with cross-functional teams (e.g., PM, design, other engineers) and how you influenced without authority
  • Alignment with Microsoft's culture: customer obsession, diversity and inclusion, one Microsoft, growth mindset
  • Lessons learned and how you applied them to future projects

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

Q2

Implement an LFU cache with get(key) and put(key, value) operations, both in O(1) average time. On capacity overflow, evict the least frequently used key, breaking ties by evicting the least recently used among keys with the minimum frequency.

Algorithms & Data Structures
Author's notes

This one took me a minute to get oriented.

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AI HintsAI Generated

Suggested Approach

Design a data structure combining a hash map for O(1) key lookup and a frequency-indexed doubly linked list to maintain access order within each frequency. Use a min-frequency pointer to track the least frequently used group, updating it on insertions and evictions. Clearly explain how get and put operations maintain O(1) average time by moving nodes between frequency lists and evicting the LRU node from the min-frequency list when capacity is exceeded.

Pro tip: Mention that using a doubly linked list for each frequency allows O(1) removal and insertion, and that the min-frequency pointer avoids scanning for the minimum. Also, clarify that 'average O(1)' assumes hash map operations are O(1) on average, and discuss potential worst-case scenarios if needed.

1. Clarify requirements and constraints

Confirm that both get and put must be O(1) average time, and that eviction is LFU with LRU tie-breaking. Ask about cache size limits and whether keys/values are integers or generic.

2. Choose data structures

Use a hash map (key -> node) for O(1) access. Maintain a doubly linked list per frequency to track LRU order. Keep a min_freq variable to quickly find the least frequently used list.

3. Define node structure and operations

Each node stores key, value, frequency, and prev/next pointers. For get, if key exists, increment its frequency and move it to the appropriate frequency list. For put, update existing key or insert new key with frequency 1; if capacity exceeded, evict the LRU node from the min_freq list.

4. Handle edge cases and updates

When moving a node to a new frequency, remove it from the old list and add to the new list (creating the list if needed). Update min_freq when the old list becomes empty or when inserting a new key. Ensure eviction updates the hash map and min_freq correctly.

5. Analyze complexity and test

Argue that each operation involves O(1) hash map lookups and O(1) linked list manipulations, so average time is O(1). Walk through an example to verify correctness, especially tie-breaking and min_freq updates.

Key Points to Mention

  • Hash map for O(1) key lookup and node access.
  • Doubly linked list per frequency to maintain LRU order within each frequency.
  • Min-frequency pointer to track the least frequently used group for O(1) eviction.
  • Node movement between frequency lists on access or update.
  • Eviction policy: remove LRU node from the min-frequency list when capacity is exceeded.
  • Time complexity: O(1) average for both get and put due to constant-time hash and list operations.

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