Amazon Coding Assessment Preparation: Data Structures, Algorithms, and Interview Tips

Amazon's software engineering hiring process includes an online coding assessment (OA) with 2 algorithm problems to solve in 70-90 minutes, followed by a work style assessment and virtual or on-site interviews. The coding problems test core data structures (arrays, hash maps, trees, graphs) and algorithm patterns (BFS/DFS, sliding window, dynamic programming). Candidates who practice 100-200 LeetCode problems over 4-8 weeks and study Amazon's Leadership Principles have the highest success rates.

Online Assessment Format

The Amazon coding assessment online assessment (OA) is the first technical hurdle for software development engineer (SDE) candidates. Understanding the format removes uncertainty and helps you focus on execution.

Structure of the Online Assessment:

The OA is typically divided into two main sections:

Section 1: Coding Problems (70-90 minutes)

You receive 2 algorithm problems to solve in a code editor with a built-in test runner. The problems typically range from LeetCode Medium to Hard difficulty. You can use your preferred programming language. The environment provides sample test cases, but your solution is evaluated against hidden test cases after submission.

Key characteristics of Amazon OA coding problems:

• Problem 1 is usually a medium-difficulty problem solvable with fundamental data structures (arrays, hash maps, sorting)
• Problem 2 is typically harder, requiring knowledge of graphs, dynamic programming, or advanced algorithmic patterns
• Problems are often disguised as Amazon-themed scenarios (package delivery routes, warehouse optimization, product recommendations)
• Both optimal time complexity and correct output are evaluated — brute force solutions may time out on large inputs

Section 2: Work Style Assessment (~20 minutes)

After the coding section, you complete a behavioral assessment with situational judgment questions aligned to Amazon's Leadership Principles. This is the same work style assessment used for non-technical roles. Do not skip or rush this section — it factors into your overall evaluation.

What Amazon Is Measuring:

• Problem-solving ability — Can you break down complex problems into manageable steps?
• Code quality — Is your code clean, readable, and well-structured?
• Algorithmic efficiency — Does your solution use optimal time and space complexity?
• Edge case handling — Do you account for empty inputs, boundary values, and unusual scenarios?
• Cultural fit — Does your work style assessment align with Amazon's Leadership Principles?

Test your general Amazon knowledge with our Amazon Knowledge practice quiz to understand the broader business context.

Essential Data Structures and Algorithms

The Amazon coding assessment draws heavily from a specific set of data structures and algorithm patterns. Mastering these covers approximately 80% of the problems you will encounter.

Tier 1: Must-Know Data Structures

Tier 2: Must-Know Algorithm Patterns

• Two Pointers / Sliding Window: Used for substring problems, subarray sums, and container problems. Practice: longest substring without repeating characters, minimum window substring, container with most water.
• BFS / DFS: Graph traversal is one of the most common Amazon OA topics. Practice: number of islands, rotting oranges, word ladder, clone graph. BFS is preferred for shortest path problems; DFS for exhaustive search.
• Dynamic Programming: Appears in harder problems. Start with 1D DP (climbing stairs, coin change), then move to 2D DP (longest common subsequence, unique paths). Amazon DP problems often involve optimization — minimizing cost or maximizing profit.
• Binary Search: Not just for sorted arrays — binary search on the answer space is a powerful technique. Practice: search in rotated sorted array, find peak element, capacity to ship packages within D days.
• Greedy Algorithms: Used when locally optimal choices lead to globally optimal solutions. Practice: meeting rooms, task scheduler, minimum number of platforms.
• Union-Find (Disjoint Set): Appears in connectivity problems. Practice: number of connected components, accounts merge, redundant connection.

Most Frequently Asked Amazon Problem Types:

1. Graph traversal (BFS/DFS) — delivery optimization, network connectivity
2. Array manipulation — two pointers, sliding window, prefix sums
3. Tree traversal — binary tree operations, BST validation
4. Dynamic programming — optimization problems, string matching
5. Hash map applications — grouping, frequency analysis, anagram detection

Behavioral and Leadership Principles

Technical skills alone will not get you hired at Amazon. The behavioral component — both in the work style assessment and in interview rounds — carries significant weight. Amazon is one of the few major tech companies that will reject technically strong candidates who do not demonstrate alignment with their Leadership Principles.

The 5 Most Tested Leadership Principles:

1. Customer Obsession

"Leaders start with the customer and work backwards." Every decision should consider customer impact. In interviews, demonstrate that you think about end-user experience when designing solutions, not just technical elegance.

2. Ownership

"Leaders act on behalf of the entire company, beyond just their own team. They never say 'that's not my job.'" Show examples where you took initiative beyond your assigned responsibilities, fixed problems you discovered even if they were not yours to fix, and thought about long-term consequences.

3. Bias for Action

"Speed matters in business. Many decisions and actions are reversible and do not need extensive study." Amazon values calculated risk-taking over analysis paralysis. Show that you make decisions with incomplete information when waiting would cost more than being wrong.

4. Deliver Results

"Leaders focus on the key inputs for their business and deliver them with the right quality and in a timely fashion." Have concrete examples of projects you delivered on time, obstacles you overcame, and metrics that demonstrate impact.

5. Earn Trust

"Leaders listen attentively, speak candidly, and treat others respectfully." This principle tests self-awareness and honesty. Be prepared to discuss mistakes you have made, how you handled disagreements, and how you built trust with team members.

Preparing Behavioral Answers (STAR Method):

Amazon interviewers expect answers structured using the STAR method:

• Situation: Briefly describe the context
• Task: What was your specific responsibility?
• Action: What did you do? (Focus on YOUR actions, not the team's)
• Result: What was the outcome? Use metrics when possible

Prepare 8-10 STAR stories that map to different Leadership Principles. Each story should be 2-3 minutes when told aloud. Practice until they feel natural — rehearsed but not robotic.

Build your understanding of Amazon's ecosystem with our FBA Seller Quiz — demonstrating knowledge of Amazon's business model strengthens your behavioral answers.

Preparation Strategy and Timeline

A structured preparation plan for the Amazon coding assessment and subsequent interview loop should span 4-8 weeks depending on your current skill level.

4-Week Intensive Plan (for experienced developers):

Week 1: Foundation

• Review core data structures: arrays, hash maps, stacks, queues, trees, graphs
• Solve 5 easy LeetCode problems per day to build fluency
• Study Amazon's Leadership Principles — read each with examples

Week 2: Pattern Recognition

• Focus on algorithm patterns: two pointers, sliding window, BFS/DFS, binary search
• Solve 3-4 medium LeetCode problems per day
• Begin writing STAR stories for behavioral questions

Week 3: Advanced Topics

• Tackle dynamic programming, greedy algorithms, and union-find
• Solve 2-3 hard LeetCode problems per day
• Practice mock interviews with a partner or platform like Pramp/interviewing.io

Week 4: Simulation and Review

• Take timed mock OAs (use LeetCode contest mode or HackerRank)
• Review all problems you struggled with — identify patterns in your mistakes
• Finalize and rehearse 8-10 STAR stories
• Rest the day before your assessment

8-Week Relaxed Plan (for less experienced developers):

• Weeks 1-2: Review fundamentals, solve easy problems, study language-specific syntax
• Weeks 3-4: Core algorithm patterns with medium problems
• Weeks 5-6: Advanced algorithms with hard problems and pattern practice
• Week 7: Mock assessments and behavioral preparation
• Week 8: Review, simulate, and rest

Recommended Practice Platforms:

• LeetCode — Filter by "Amazon" tag to find problems frequently asked in Amazon interviews. Premium membership unlocks company-specific problem frequency data.
• HackerRank — Amazon uses a similar interface for its OA. Practicing on HackerRank familiarizes you with the coding environment.
• NeetCode.io — Curated list of 150 essential problems organized by pattern. The NeetCode 150 covers virtually every pattern Amazon tests.
• Blind 75 — The classic list of 75 most common interview problems across all major tech companies.

During the Assessment:

• Read both problems before starting — solve the easier one first to secure partial credit
• Write pseudocode before coding — plan your approach before touching the keyboard
• Test with edge cases: empty input, single element, very large input, negative numbers
• If your optimal solution is not working, submit a correct brute-force solution — partial credit for passing some test cases is better than zero
• Watch your time — if Problem 1 takes 30 minutes, you need 40-60 minutes for Problem 2