Amazon SDE-2 Interview Questions and Answers for Freshers

Round duration - 60 minutes
Round difficulty - Medium

It was a telephonic interview at 10 in the morning. Interviewer seemed cool.

Q1. 
Best Insert Position for a Target in a Sorted Array
You are provided with a sorted array A of length N consisting of distinct integers and a target integer M. Your task is to determine the position where ...read more
Ans. 
Find the best insert position for a target in a sorted array to maintain order.
• Use binary search to find the correct position for the target integer in the sorted array.

• If the target is already present in the array, return its index.

• Maintain the sorted order of the array after inserting the target integer.

• Handle edge cases like empty array or target being smaller than the first element or larger than the last element.
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Round duration - 60 minutes
Round difficulty - Medium

The interview was in the morning at 10 AM in the office meeting room.

Q1. 
House Robber Problem Statement
Mr. X is a professional robber with a plan to rob houses arranged in a circular street. Each house has a certain amount of money hidden, separated by a security system that ...read more
Ans. 
House Robber problem - find maximum amount of money Mr. X can rob without triggering alarm in circular street.
• Use dynamic programming to keep track of maximum money robbed at each house.

• Consider two cases - robbing the first house and not robbing the first house.

• Handle circular arrangement by considering the first and last houses separately.

• Return the maximum amount of money that can be robbed without triggering the al...read more
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Round duration - 60 minutes
Round difficulty - Medium

The interview was at 11 AM in the meeting office.

Q1. 
Running Median Problem
Given a stream of integers, calculate and print the median after each new integer is added to the stream.
Output only the integer part of the median.
Example:
Input:
N = 5  
Stre...read more
Ans. 
Calculate and print the median after each new integer is added to the stream.
• Use a min heap to store the larger half of the numbers and a max heap to store the smaller half of the numbers.

• Keep the two heaps balanced by ensuring the size difference is at most 1.

• If the total number of elements is odd, the median is the top element of the larger heap. If even, it's the average of the tops of both heaps.
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Round duration - 60 minutes
Round difficulty - Medium

The interview was at 1 AM.

Round duration - 60 minutes
Round difficulty - Easy

The meeting was at 2 PM in the office meeting room.

Round duration - 60 minutes
Round difficulty - Easy

10 AM

Q1. Can you provide a deeper discussion about all the projects you completed in your previous company?
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Round duration - 60 minutes
Round difficulty - Easy

The first round was a coding round. 2 DSA based questions were asked.

Q1. 
Maximum Meetings Problem Statement
Given the schedule of N meetings with their start time Start[i] and end time End[i], you need to determine which meetings can be organized in a single meeting room such ...read more
Ans. 
Given N meetings with start and end times, determine which meetings can be organized in a single room to maximize the number of meetings.
• Sort the meetings based on their end times.

• Iterate through the sorted meetings and select the first meeting that does not overlap with the previous one.

• Repeat the process until all meetings are considered.

• Return the selected meetings in the order they are organized.
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Q2. 
Peak Element Finder
For a given array of integers arr, identify the peak element. A peak element is an element that is greater than its neighboring elements. Specifically, if arr[i] is the peak, then both...read more
Ans. 
Find the peak element in an array of integers.
• Iterate through the array and check if the current element is greater than its neighbors.

• Handle edge cases for the first and last elements of the array.

• Return the peak element found.
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Round duration - 45 minutes
Round difficulty - Medium

The second round was a system design round.

Round duration - 30 minutes
Round difficulty - Easy

This was a typical managerial round.

Q1. Data structure related question
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Q1. Nodejs related questions
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Q2. Promises Async Await Events emitter
Ans. 
Promises, async/await, and event emitters are all ways to handle asynchronous operations in JavaScript.
• Promises provide a way to handle asynchronous operations by returning a promise object that can be resolved or rejected.

• Async/await is a syntax for working with promises that makes code easier to read and write.

• Event emitters allow you to create custom events that can be triggered and listened for in your code.
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Q1. System design related question
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Q2. Design a system like facebook
Ans. 
Design a system like Facebook
• Create a user registration and login system

• Implement a news feed for users to see updates from friends

• Allow users to create and join groups

• Include features like messaging, commenting, and liking posts

• Implement privacy settings for users to control who can see their content
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Q1. System design and behavioral
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Round duration - 60 Minutes
Round difficulty - Medium

This was a Data Structures and Algorithms round with preety good questions . I was expected to come up with an efficient approach and code it as well .

Q1. 
K Closest Points to Origin Problem Statement
Your house is located at the origin (0,0) of a 2-D plane. There are N neighbors living at different points on the plane. Your goal is to visit exactly K neighb...read more
Ans. 
Find the K closest points to the origin in a 2-D plane using Euclidean Distance.
• Calculate the Euclidean Distance of each point from the origin

• Sort the points based on their distances

• Return the first K points as the closest neighbors
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Q2. 
Power Set Generation
Given a sorted array of 'N' integers, your task is to generate the power set for this array. Each subset of this power set should be individually sorted.
A power set of a set 'ARR' i...read more
Ans. 
Generate the power set of a sorted array of integers with individually sorted subsets.
• Use recursion to generate all possible subsets by including or excluding each element in the array.

• Sort each subset before adding it to the power set.

• Handle base cases for empty array and single element array.

• Ensure the subsets are unique by using a set data structure.

• Time complexity can be exponential due to the nature of generating ...read more
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Round duration - 50 Minutes
Round difficulty - Hard

This was also a DSA round where I was asked to code only one of the questions but I eventually ended up coding both as I had some spare time and explained my approches very smoothly to the interviewer . This round went preety well .

Q1. 
Roman Numeral to Integer Conversion
Convert a string representing a Roman numeral into its integer equivalent and return the result.
Explanation:
Roman numerals are represented by seven different symbol...read more
Ans. 
Convert a Roman numeral string to its integer equivalent.
• Create a mapping of Roman numeral symbols to their integer values.

• Iterate through the input string and add the corresponding integer values.

• Handle cases where subtraction is needed (e.g., IV = 4, IX = 9).
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Q2. 
Pair Sum Problem Statement
You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to find and return a list of all pairs of elements where each sum of a pair equals 'S'.
Note:
...read more
Ans. 
Find pairs of elements in an array that sum up to a given value, sorted in a specific order.
• Iterate through the array and for each element, check if the complement (S - current element) exists in a hash set.

• If the complement exists, add the pair to the result list.

• Sort the result list based on the criteria mentioned in the question.

• Return the sorted list of pairs.
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Round duration - 50 Minutes
Round difficulty - Medium

This was also a DSA round with 2 questions . One was implementation heavy and the other was related to recursion and so I handled it carefully so that my code does not run into TLE or Segmentation Fault.

Q1. 
Arithmetic Expression Evaluation Problem Statement
You are provided with a string expression consisting of characters '+', '-', '*', '/', '(', ')' and digits '0' to '9', representing an arithmetic express...read more
Ans. 
Evaluate arithmetic expressions in infix notation with given operators and precedence rules.
• Parse the infix expression to postfix using a stack.

• Evaluate the postfix expression using a stack.

• Handle operator precedence and parentheses while evaluating.

• Ensure no division by zero cases and operands fit in 32-bit integer.
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Q2. 
Remove Duplicates from Sorted Array Problem Statement
You are given a sorted integer array ARR of size N. Your task is to remove the duplicates in such a way that each element appears only once. The outpu...read more
Ans. 
Remove duplicates from a sorted array in-place with O(1) extra memory.
• Use two pointers - one for iterating through the array and another for placing unique elements.

• Compare current element with next element to identify duplicates and skip them.

• Update array in-place by moving unique elements to the front.

• Return the length of the array after removal of duplicates.
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Round duration - 50 Minutes
Round difficulty - Medium

This was a typical System Design round where I was asked about the various features of Facebook and what sort of data structures and algorithms are used in implementing them .

Q1. How does Facebook store likes and dislikes?
Ans. 
Facebook stores likes and dislikes using a combination of databases and algorithms.
• Likes and dislikes are stored in databases such as MySQL or Cassandra.

• Algorithms are used to analyze user behavior and recommend content based on likes and dislikes.

• User interactions with posts, pages, and ads are tracked to determine likes and dislikes.

• Likes and dislikes may also be used to personalize the user's feed and target ads mor...read more
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Q2. How does Facebook implement graph search?
Ans. 
Facebook implements graph search using a graph database to efficiently search for connections between users and their interests.
• Facebook uses a graph database to store connections between users, pages, groups, etc.

• The graph search algorithm traverses the graph to find relevant connections based on user queries.

• It takes into account factors like user relationships, interests, and interactions to provide personalized sea...read more
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Round duration - 50 Minutes
Round difficulty - Medium

This was a preety intense round as I was grilled more on my System Design concepts but eventually I was able to asnwers all the questions with some help from the interviewer.

Q1. What is Hadoop and why is it used?
Ans. 
Hadoop is a framework for distributed storage and processing of large data sets.
• Hadoop is used for storing and processing big data across a distributed network of computers.

• It is based on the MapReduce programming model, which allows for parallel processing of data.

• Hadoop consists of HDFS for storage and YARN for resource management.

• It is used for tasks like data warehousing, log processing, recommendation systems, and...read more
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Q2. How does Facebook Chat work?
Ans. 
Facebook Chat works by using a combination of websockets, long polling, and push technology to deliver real-time messaging.
• Facebook Chat uses websockets for real-time communication between the client and server.

• Long polling is used to check for new messages when websockets are not supported.

• Push technology is used to notify users of new messages even when the chat window is not open.

• Messages are stored in a database an...read more
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