AMAZON PHONE SCREENING INTERVIEW FOR GRAD SDE ROLE

1. Introduction

• The interviewer introduced himself.
• He asked me to introduce myself.
• Immediately transitioned to coding without much small talk.

2. Coding Question 1 — One Missing Number

Problem:
Find the missing number from a continuous vector of numbers.

My Response:

• Asked about edge cases.
• Wrote a brute-force approach and explained:
  • Time Complexity and Space Complexity
• Mentioned that it could be optimized.
• Interviewer stopped me from writing optimized code and asked for verbal explanation.

Optimized Approach (Verbal):

• Explained the optimized approach clearly.
• Discussed:
  • Time Complexity and Space Complexity
• Interviewer was satisfied with the explanation.

3. Follow-up — Two Missing Numbers

Problem Update:
Now two numbers were missing from a continuous array.

Discussion:

• He asked whether the brute-force approach would still work.
• I confirmed that it would.
• He then asked me to write the most optimized approach for this case.

My Response:

• Wrote the optimized solution.
• Discussed:
  • Time Complexity and Space Complexity along with code structure
• Had a short discussion on trade-offs.
• Interviewer was satisfied.

4. Conceptual Question — Hash Map Lookup

Question:
What is the time complexity to search an element in a hash map?

My Answer:

• For map in C++ → O(log n) (uses Red-Black Tree).
• For unordered_map → O(1) average (uses hashing).

Follow-up:

• Explained the difference between map and unordered_map.
• Interviewer seemed happy with the answer.

5. Wrap-up

• Interview ended due to time constraints.
• I asked him:

  “When was the last time you implemented or used a high-level data structure?”

His Response:

• Described a recent real-world scenario involving maps.

Summary

• Focused mainly on:
  • Coding skills
  • Optimizing solutions
  • Analyzing time & space complexities
• Interviewer appreciated verbal clarity and quick thinking.