What are Amazon coding interview questions?

Amazon is renowned for its rigorous and comprehensive interview process, particularly for technical roles such as Software Development Engineer (SDE). Preparing for an Amazon coding interview involves understanding the types of questions you might encounter, the underlying principles Amazon values, and effective strategies to showcase your skills and fit for the company. Here's a detailed overview to help you navigate and excel in Amazon's coding interviews:

1. Overview of Amazon Coding Interviews

Amazon’s coding interviews are designed to assess your problem-solving abilities, technical expertise, and alignment with Amazon’s Leadership Principles. The interview process typically includes multiple stages:

1. Online Assessment (OA):

   • Format: Timed coding challenges, often using platforms like HackerRank or Amazon's proprietary tools.
   • Focus: Algorithms, data structures, and problem-solving skills.
   • Duration: Approximately 1-2 hours.

2. Phone Screens:

   • Format: One or two technical interviews conducted via phone or video call.
   • Focus: Coding problems, often shared via a collaborative editor.
   • Duration: 45-60 minutes each.

3. Onsite Interviews (Virtual or In-Person):

   • Format: Multiple back-to-back interviews, typically 4-6 rounds.
   • Focus: A mix of coding, system design (for senior roles), and behavioral questions aligned with Amazon’s Leadership Principles.
   • Duration: Each interview lasts about 45-60 minutes.

2. Types of Coding Interview Questions

Amazon's coding interviews cover a range of topics to evaluate different aspects of your technical abilities:

a. Data Structures and Algorithms

These questions assess your understanding and application of fundamental computer science concepts.

• Arrays and Strings:

  • Example: "Given an array of integers, find two numbers that add up to a specific target."

• Linked Lists:

  • Example: "Implement a function to reverse a singly linked list."

• Trees and Graphs:

  • Example: "Find the maximum depth of a binary tree."

• Stacks and Queues:

  • Example: "Evaluate the value of an arithmetic expression in Reverse Polish Notation."

• Hash Tables:

  • Example: "Find the first non-repeating character in a string."

• Dynamic Programming:

  • Example: "Given a list of numbers, find the length of the longest increasing subsequence."

b. System Design (for Senior Roles)

For senior engineering positions, Amazon emphasizes your ability to design scalable and efficient systems.

• Example Questions:
  • "Design a scalable URL shortening service like bit.ly."
  • "How would you design Amazon’s recommendation system?"

c. Behavioral Questions Aligned with Leadership Principles

Amazon places significant emphasis on its Leadership Principles, which guide the company’s culture and decision-making. Behavioral questions aim to assess how well you embody these principles.

• Example Questions:
  • "Tell me about a time you took ownership of a project." (Ownership)
  • "Describe a situation where you had to dive deep to solve a problem." (Dive Deep)
  • "Give an example of how you handled a conflict within your team." (Earn Trust)

3. Sample Amazon Coding Interview Questions

Here are some illustrative examples of questions you might encounter:

a. Coding Questions

1. Two Sum

   • Problem: Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
   • Example Input: nums = [2, 7, 11, 15], target = 9
   • Example Output: [0, 1]

2. Longest Substring Without Repeating Characters

   • Problem: Given a string, find the length of the longest substring without repeating characters.
   • Example Input: "abcabcbb"
   • Example Output: 3 (The answer is "abc")

3. Merge Two Sorted Lists

   • Problem: Merge two sorted linked lists and return it as a new sorted list.
   • Example Input: 1->2->4, 1->3->4
   • Example Output: 1->1->2->3->4->4

4. Valid Parentheses

   • Problem: Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
   • Example Input: "()[]{}"
   • Example Output: True

b. System Design Questions

1. Design a URL Shortening Service

   • Focus Areas: Database schema design, unique ID generation, scalability, caching strategies, handling high traffic, and ensuring data consistency.

2. Design Amazon’s Review System

   • Focus Areas: Handling large-scale data, real-time updates, user authentication, spam detection, and ensuring system reliability.

c. Behavioral Questions

1. Ownership

   • Question: "Tell me about a time you took ownership of a project outside your usual responsibilities."
   • What Interviewers Look For: Initiative, responsibility, and the ability to drive projects to completion.

2. Customer Obsession

   • Question: "Describe a time when you went above and beyond to meet a customer’s needs."
   • What Interviewers Look For: Dedication to customer satisfaction and problem-solving skills.

4. Preparation Strategies

To excel in Amazon's coding interviews, adopt the following preparation strategies:

a. Master Data Structures and Algorithms

• Study Fundamental Concepts: Ensure a strong grasp of arrays, linked lists, trees, graphs, stacks, queues, hash tables, and dynamic programming.
• Practice Coding Problems: Use platforms like LeetCode, HackerRank, CodeSignal, and Cracking the Coding Interview to solve a wide range of problems.
• Understand Time and Space Complexity: Be able to analyze and optimize your solutions.

b. Prepare for System Design Interviews

• Learn System Design Principles: Study scalability, load balancing, database sharding, caching, microservices architecture, and fault tolerance.
• Use Frameworks: Apply structured approaches like the 4-Step System Design Process:
  1. Clarify Requirements
  2. Define High-Level Architecture
  3. Design Core Components
  4. Address Trade-offs and Bottlenecks
• Practice Designing Systems: Think through real-world systems like social networks, e-commerce platforms, and messaging services.

c. Understand Amazon’s Leadership Principles

Amazon evaluates candidates not only on technical skills but also on how well they align with its Leadership Principles. Familiarize yourself with these principles and prepare examples from your experience that demonstrate them.

• Learn the Principles: Examples include Customer Obsession, Ownership, Invent and Simplify, and Dive Deep.
• Use the STAR Method: Structure your behavioral responses using Situation, Task, Action, and Result to clearly convey your experiences.

d. Conduct Mock Interviews

• Simulate Real Interviews: Practice with peers, mentors, or use online platforms like Pramp, DesignGurus.io, or LeetCode’s Interview Simulator.
• Seek Feedback: Use feedback to identify areas for improvement and refine your approach.

e. Review Past Projects and Experiences

• Be Ready to Discuss: Clearly articulate your role, the challenges you faced, the actions you took, and the outcomes.
• Highlight Achievements: Use quantifiable results to demonstrate your impact.

5. During the Interview

a. Communicate Clearly and Effectively

• Explain Your Thought Process: As you solve coding problems, articulate your reasoning and approach.
• Ask Clarifying Questions: Ensure you fully understand the problem before diving into coding.

b. Write Clean and Efficient Code

• Follow Best Practices: Use meaningful variable names, proper indentation, and comments where necessary.
• Optimize Solutions: Strive for the most efficient solution in terms of time and space complexity.

c. Handle Behavioral Questions with Confidence

• Be Honest and Authentic: Share genuine experiences and lessons learned.
• Align with Leadership Principles: Demonstrate how your actions reflect Amazon’s values.

6. After the Interview

a. Send a Thank-You Note

• Express Gratitude: Thank the interviewers for their time and the opportunity.
• Reiterate Interest: Reinforce your enthusiasm for the role and the company.

Example Thank-You Message:

Subject: Thank You for the [Job Title] Interview

Hi [Interviewer’s Name],

I wanted to thank you for taking the time to interview me for the [Job Title] position at Amazon today. I enjoyed our discussion about [specific topic] and am excited about the opportunity to contribute to your team.

Please let me know if there’s any additional information I can provide.

Best regards,
[Your Name]

b. Reflect on Your Performance

• Identify Strengths and Weaknesses: Consider what went well and what could be improved for future interviews.
• Seek Feedback: If possible, ask for feedback to understand areas for growth.

7. Additional Resources

• Books:

  • "Cracking the Coding Interview" by Gayle Laakmann McDowell
  • "Elements of Programming Interviews" by Adnan Aziz, Tsung-Hsien Lee, and Amit Prakash

• Online Platforms:

  • LeetCode: Extensive collection of coding problems.
  • HackerRank: Coding challenges and contests.
  • System Design Primer: Comprehensive guide on system design.

• Courses:

  • Coursera’s Algorithms Specialization
  • Udemy’s System Design Courses

Conclusion

Preparing for an Amazon coding interview requires a balanced focus on technical skills, problem-solving abilities, and alignment with Amazon’s Leadership Principles. By thoroughly understanding the interview process, practicing a wide range of coding problems, refining your system design skills, and preparing thoughtful behavioral responses, you can enhance your chances of success. Remember to communicate clearly, stay calm under pressure, and demonstrate both your technical prowess and cultural fit for Amazon.