Amazon SDE-2 Interview Questions and Answers

Q1. Behavioural questions related to leadership principle.
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Round duration - 60 Minutes
Round difficulty - Medium

Timing: 10AM-11AM
Interviewer was quite supportive and helpful.
Environment was normal as usual and it was morning time

Round duration - 60 Minutes
Round difficulty - Medium

Timing: 11AM-12PM
The interviewer was SDE2
He was checking the code for edge cases and was hinting if required

Q1. 
Implementing a Priority Queue Using Heap
Ninja has been tasked with implementing a priority queue using a heap data structure. However, he is currently busy preparing for a tournament and has requested yo...read more
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Q2. 
Ninja and the Bulbs Challenge
Ninja owns an electronic shop and possesses 'N' bulbs. To verify the quality of the bulbs, Ninja performs a unique technique. After 'N' rounds of this process, bulbs that rem...read more
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Round duration - 60 Minutes
Round difficulty - Medium

Timing: 6PM-7PM
The interviewer was not interactive and didn't gave any feedback whatsoever.
It was Hiring Manager Round
Interviewer was Software Development Manager at Amazon

Q1. 
Maximize the Sum Through Two Arrays
You are given two sorted arrays of distinct integers, ARR1 and ARR2. If there is a common element in both arrays, you can switch from one array to the other.
Your task...read more
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Round duration - 60 minutes
Round difficulty - Easy

Started with brief intro(5 mins) about interviewer.
Problem solving question, question was already there in the codelink shared by the interviewer. He explained the problem again with sample testcase. 
The Interviewer was friendly.

Q1. 
Course Schedule II Problem Statement
You are provided with a number of courses 'N', some of which have prerequisites. There is a matrix named 'PREREQUISITES' of size 'M' x 2. This matrix indicates that fo...read more
Ans. 
Given courses with prerequisites, determine a valid order to complete all courses.
• Create a graph with courses as nodes and prerequisites as edges.

• Use topological sorting to find a valid order to complete all courses.

• Return an empty list if it's impossible to complete all courses.
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Q2. Design a live video broadcast platform.
Ans. 
Design a live video broadcast platform.
• Implement video streaming functionality using protocols like RTMP or WebRTC

• Include features for live chat, reactions, and audience engagement

• Ensure scalability and reliability by using cloud services like AWS or Azure

• Provide analytics for viewership data and user engagement

• Integrate monetization options such as ads or subscriptions
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Round duration - 90 minutes
Round difficulty - Medium

There were 2 interviewers(India HM and Seattle HM), India HM was just shadowing and didn't ask any questions. Started with intro, he asked in detail about what I do at current company(10 mins). Again, jumped into LP's(25 mins).

Q1. 
Distance Between Two Nodes in a Binary Tree
Given a binary tree and the values of two distinct nodes, determine the distance between these two nodes in the tree. The distance is defined as the minimum num...read more
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Q2. 
Median in a Stream Problem Statement
Your task is to determine the median of integers as they are read from a data stream. The median is the middle value in the ordered list of numbers. If the list length...read more
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Round duration - 60 minutes
Round difficulty - Medium

There was only 1 interviewer in this round and We had no video sharing in this round so it was becoming difficult to understand each other.

Round duration - 45 minutes
Round difficulty - Medium

This round was scheduled in the evening hours and all the participants were required to fill a form which was shared 15 minutes prior to the start of the online coding round. This form was filled out probably for the security reasons and to ensure that no one disinterested participant gives the test.

Q1. 
Ways To Make Coin Change
Given an infinite supply of coins of varying denominations, determine the total number of ways to make change for a specified value using these coins. If it's not possible to make...read more
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Q2. 
Validate Binary Search Tree (BST)
You are given a binary tree with 'N' integer nodes. Your task is to determine whether this binary tree is a Binary Search Tree (BST).
BST Definition:
A Binary Search Tr...read more
Ans. 
Validate if a given binary tree is a Binary Search Tree (BST) or not.
• Check if the left subtree of a node contains only nodes with data less than the node's data

• Check if the right subtree of a node contains only nodes with data greater than the node's data

• Recursively check if both left and right subtrees are also binary search trees
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Round duration - 60 minutes
Round difficulty - Hard

This round was on call where I was just supposed to answer the tech questions that were asked. It started with a brief interview with one another and then moved to questions on DBMS, operating systems, computer networks and all. Almost 20-25 questions were asked and I probably answered 90% of them correctly.

Q1. 
Reverse Linked List Problem Statement
Given a Singly Linked List of integers, your task is to reverse the Linked List by altering the links between the nodes.
Input:
The first line of input is an intege...read more
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Round duration - 30 minutes
Round difficulty - Hard

There was only one interviewer for this round. He continuously interacted with me and was giving me some good situational problems that were not very easy to answer. Basically those were open-minded questions which can be answered oth ways and that's why I found it quiet hard as per my nature but at the end things went well for me.

Round duration - 90 minutes
Round difficulty - Easy

I got a call from an Amazon recruiter regarding the schedule of the test . She sent me the coding test link which I had to complete within a week. we can attempt the online test anytime, when we have time for a period of 90 minutes at a stretch.Once I completed the test, I got a call to schedule the interviews in two weeks.

Q1. 
Shopping Options Problem Statement
Given arrays representing the costs of pants, shirts, shoes, and skirts, and a budget amount 'X', determine the total number of valid combinations that can be purchased ...read more
Ans. 
Determine total number of valid shopping combinations within budget
• Iterate through all possible combinations of items from each array

• Check if the total cost of the combination is within the budget

• Return the count of valid combinations
Answered by AI
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Q2. 
Max Submatrix Problem Statement
You are provided with a matrix MAT consisting of integers, with dimensions N x M (i.e., N rows and M columns). Your objective is to determine the maximum sum submatrix with...read more
Ans. 
Find the maximum sum submatrix in a given matrix.
• Iterate over all possible submatrices and calculate their sums

• Use Kadane's algorithm to find the maximum sum subarray in each row

• Combine the sums of rows to find the maximum sum submatrix
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Round duration - 60 minutes
Round difficulty - Medium

Virtual interview occured in amazon chime.The interviewer gave his introduction, asked me a bit on the kind of projects I’ve worked on. Then he started with a data structure problem.

Q1. 
Clone a Binary Tree with Random Pointers
Given a binary tree where each node has pointers to its left, right, and a random node, create a deep copy of the binary tree.
Input:
The first line contains an ...read more
Ans. 
Clone a binary tree with random pointers and verify if cloning was successful by printing inorder traversal.
• Create a deep copy of the binary tree with random pointers.

• Print the inorder traversal of the cloned binary tree.

• Verify cloning success by printing '1' if successful, '0' otherwise.
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Q2. 
The Ninja Port Problem
Ninja is in a city with 'N' colonies, where each colony contains 'K' houses. He starts at house number "sourceHouse" in colony number "sourceColony" and wants to reach house number ...read more
Ans. 
The Ninja Port Problem involves finding the minimum time for a ninja to travel between colonies and houses using secret paths and teleportation.
• Calculate the minimum time considering teleportation within colonies, traveling between colonies, and secret paths.

• Keep track of the number of secret paths used and ensure they are one-way.

• Consider the constraints provided to optimize the solution.

• Example: N=2, K=3, S=1, P=1, s...read more
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Round duration - 75 Minutes
Round difficulty - Easy

This was taken by an engineering manager who asked me regarding my projects for around 10-15 mins and then we moved to a system design problem. He asked me to design Slack messenger.
I started by listing the functional and non-functional requirements(on which he questioned me a bit), then I moved to draw the high-level architecture. The components which I drew were the clients, gateway service(LB + authentication, etc), Messaging Service, User Service, Web Socket Manager service, Fan Out service(I added this for the group messages thing, but he didn’t interrogate much on that).

He asked me what would be the schema of my messages table and the scenarios in which the recipient user is online/offline.Also asked about the partitioning key and primary key of the 2-3 tables which I had made

Round duration - 60 minutes
Round difficulty - Hard

BarRaiser Round

This was again taken by an engineering manager who discussed my projects in depth for around 20-25 mins. In the remaining time he asked me 2 dsa questions. (Yes I too was surprised that he didn’t ask anything regarding design).

In almost all the rounds, I was asked questions related to Amazon Leadership principles, so do make sure you go through those before sitting for the interview process. You can refer to this link(https://www.codingninjas.com/codestudio/problem-lists/top-amazon-coding-interview-questions) for practicing the same, I found it useful. 
In the design rounds, interviewer doesn’t expect the most ideal answer from you and unless your choice of technology is outrageously wrong, he won’t pinpoint that.

Q1. 
Group Anagrams Together
Given an array/list of strings STR_LIST, group the anagrams together and return each group as a list of strings. Each group must contain strings that are anagrams of each other.
E...read more
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Q2. 
Add Two Numbers Represented by Linked Lists
Your task is to find the sum list of two numbers represented by linked lists and return the head of the sum list.
Explanation:
The sum list should be a linked...read more
Ans. 
Add two numbers represented by linked lists and return the head of the sum list.
• Traverse both linked lists simultaneously while keeping track of carry from previous sum

• Create a new linked list to store the sum of the two numbers

• Handle cases where one linked list is longer than the other by padding with zeros

• Update the sum and carry values accordingly while iterating through the linked lists
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Round duration - 90 minutes
Round difficulty - Medium

Q1. 
Number of Islands Problem Statement
You are provided with a 2D array or list containing 'N' rows and 'M' columns, filled with 1s and 0s. Here, 1 indicates land, and 0 indicates water.
Your task is to ide...read more
Ans. 
Count the number of islands in a 2D matrix filled with 1s and 0s.
• Iterate through the matrix and perform depth-first search (DFS) to find connected islands.

• Use a visited array to keep track of visited cells to avoid redundant calculations.

• Increment the island count whenever a new island is encountered.

• Consider all eight directions (horizontal, vertical, and diagonal) while exploring the island.

• Handle edge cases like out...read more
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Q2. 
Add First and Second Half Problem Statement
You are provided with a Singly Linked List having 'N' nodes, where each node contains a single digit.
Your task is to return a node 'X', which serves as the he...read more
Ans. 
Return a node representing the head of a new Linked List with the sum of the 1st and 2nd half of the given Linked List.
• Split the Linked List into two halves

• Reverse the 2nd half of the Linked List

• Add the corresponding digits from both halves while considering carry

• Create a new Linked List with the sum digits
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Next Greater Element Problem Statement
You are given an array arr of length N. For each element in the array, find the next greater element (NGE) that appears to the right. If there is no such greater ele...read more
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Round duration - 60 Minutes
Round difficulty - Hard

Q1. 
Word Break Problem Statement
You are given a non-empty string without spaces, referred to as 'sentence', and a list of non-empty strings representing a dictionary. Your task is to construct and return all...read more
Ans. 
Given a sentence and a dictionary, construct and return all possible sentences by inserting spaces to form words from the dictionary.
• Use backtracking to generate all possible combinations of words from the dictionary to form sentences.

• Check if a substring of the sentence matches any word in the dictionary, if so, recursively call the function with the remaining substring.

• Continue this process until the entire sentence ...read more
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Q2. 
Valid Parenthesis Problem Statement
Given a string str composed solely of the characters "{", "}", "(", ")", "[", and "]", determine whether the parentheses are balanced.
Input:
The first line contains ...read more
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Round duration - 60 minutes
Round difficulty - Easy

Q1. Design a local transport system similar to BMTC.
Ans. 
Design a local transport system similar to BMTC
• Introduce a fleet of buses covering various routes within the city

• Implement a smart card system for easy payment and tracking

• Include different types of buses like regular, AC, and Volvo for passenger comfort

• Have designated bus stops with real-time information on bus arrivals

• Offer discounted fares for students and senior citizens
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Round duration - 60 minutes
Round difficulty - Easy