Google Interview Experience (L5) — 8+ YOE

Interview Experience – L5

YOE: 8+ years
Prep time: ~4 months
Language: Java

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Qualifying Round

Question:
Implement the internal workings of a HashMap.
(The question was indirect, not "implement HashMap" literally.)

My approach:

• Explained hashing, collision resolution (separate chaining), resizing.
• Discussed load factor, capacity thresholds.
• Answered all follow-ups thoroughly.

Verdict:

• Self-assessment: ✅ Strong hire
• Actual: ✅ Passed

Notes:
Understand not just how to implement, but why you choose a collision strategy and resizing approach.

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Round 1

Question:
Given an expression, insert + and * operators to evaluate to a target.

My approach:

• Used DFS/backtracking to explore all operator placements.
• Built expression string carefully.
• Explained time and space complexity.

Follow-ups:

• Handling 0 (leading zeros).
• Handling negative numbers.

Outcome:

• Solved all parts in the interview.

Verdict:

• Self-assessment: ✅ Strong hire
• Actual: ❌ No hire

Notes:
Even if you solve the problem, interviewers will still evaluate how clearly you explain your reasoning, handle edge cases, and write clean code.

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Round 2

Question:
Given employee names with entry and exit times, for specific times, find how many employees are present.

My approach:

• Took some time clarifying the problem.
• Used sorting and line-sweep technique.
• Completed core logic.

Issue:

• Ran out of time for follow-up questions.
• Made mistakes explaining time complexity.

Verdict:

• Self-assessment: ✅ Hire
• Actual: ❌ No hire

Notes:
Make sure you can clearly and quickly explain your time/space analysis. Practice summarizing approaches like line-sweep and prefix sums under time pressure.

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Round 3

Question:
How would you implement a counter for a given userId?
(uId, counter) map

Follow-ups:
Handling in a multi-threaded environment.

My approach:

• Suggested using a basic map.
• Mentioned ConcurrentHashMap.
• Talked about AtomicInteger per user.
• Discussed synchronized blocks.

Verdict:

• Self-assessment: ✅ Hire
• Actual: ❌ No hire

Notes:
Concurrency questions often require deep understanding of Java primitives. Be ready to discuss race conditions, consistency guarantees, and practical implementation details.

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Final Verdict

• L5: ❌ No hire
• Also tried for L4: ❌ No hire

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Key Takeaways

• Master fundamentals like HashMap internals, DFS/backtracking, interval/line-sweep techniques.
• Always explain time and space complexity clearly and confidently.
• Be fast at clarifying problem statements to avoid losing time.
• Practice multi-threading patterns in your chosen language, including specifics like ConcurrentHashMap and AtomicInteger.
• Don’t just “make it work” — be able to explain why your approach is correct and optimal.