Amazon Associate Data Scientist Interview Questions and Answers

Q1. Level order tree traversal
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Q2. Find the pair element from the array
Ans. 
Find the pair element from the array
• Iterate through the array and use a hashmap to store elements and their counts

• Check if the current element's complement exists in the hashmap

• Return the pair if found, otherwise return null
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We had an aptitude test which involved 60 questions in 15 minutes. Of course, no one can solve this fast, but it was about the hit rate / accuracy and volume. Subsequent followed with two guesstimate based rounds and final as HR round which involved asking about college projects, extra curricular experiences and so on.

Q1. Where do you see yourself in 5 years
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Q1. How you will improve health of a marketplace
Ans. 
By analyzing data, identifying pain points, and implementing solutions to improve user experience and trust.
• Analyze user behavior and feedback to identify areas of improvement

• Implement measures to increase transparency and trust, such as user reviews and seller verification

• Provide resources and support for dispute resolution

• Encourage diversity and inclusivity in the marketplace to attract a wider range of buyers and se...read more
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Q1. How you will design new customer support system
Ans. 
I will design a customer support system that is user-friendly, efficient, and personalized.
• Conduct research to understand customer needs and preferences

• Identify common customer issues and develop a knowledge base for quick resolution

• Implement a ticketing system to track and prioritize customer inquiries

• Integrate chatbots and AI to provide 24/7 support

• Train support staff to provide personalized and empathetic service

• Col...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This was a typical DS/Algo where I was asked to solve two questions related to Binary Trees and write the pseudo code for both of them followed by some theoretical questions related to Operating Systems.

Q1. 
K-th Largest Number in a BST
Given a binary search tree (BST) consisting of integers and containing 'N' nodes, your task is to find and return the K-th largest element in this BST.
If there is no K-th la...read more
Ans. 
Find the K-th largest element in a BST.
• Perform reverse in-order traversal of the BST to find the K-th largest element.

• Keep track of the count of visited nodes to determine the K-th largest element.

• Return -1 if there is no K-th largest element in the BST.
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Q2. 
Is Height Balanced Binary Tree Problem Statement
Determine if the given binary tree is height-balanced. A tree is considered height-balanced when:
1. The left subtree is balanced.
2. The right subtree is bala...read more
Ans. 
Determine if a given binary tree is height-balanced by checking if left and right subtrees are balanced and their height difference is at most 1.
• Check if the left subtree is balanced

• Check if the right subtree is balanced

• Calculate the height difference between the left and right subtrees

• Return 'True' if all conditions are met, otherwise return 'False'
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Q3. Can you explain the concepts of Zombie Process and Orphan Process in operating systems?
Ans. 
Zombie process is a terminated process that has completed execution but still has an entry in the process table. Orphan process is a process whose parent process has terminated.
• Zombie process is created when a child process completes execution but its parent process has not yet read its exit status.

• Zombie processes consume system resources and should be cleaned up by the parent process using wait() system call.

• Orphan p...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This was also a Data Structures and Algorithm round where I was asked to solve 3 medium to hard level problems along with their pseudo code within 60 minutes .

Q1. 
Longest Substring Without Repeating Characters Problem Statement
Given a string S of length L, determine the length of the longest substring that contains no repeating characters.
Example:
Input:
"abac...read more
Ans. 
Find the length of the longest substring without repeating characters in a given string.
• Use a sliding window approach to keep track of the longest substring without repeating characters.

• Use a hashmap to store the index of each character in the string.

• Update the start index of the window when a repeating character is found.

• Calculate the maximum length of the window as you iterate through the string.

• Return the maximum le
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Q2. 
Problem: Search In Rotated Sorted Array
Given a sorted array that has been rotated clockwise by an unknown amount, you need to answer Q queries. Each query is represented by an integer Q[i], and you must ...read more
Ans. 
Search for integers in a rotated sorted array efficiently.
• Use binary search to efficiently search for integers in the rotated sorted array.

• Handle the rotation of the array while performing binary search.

• Return the index of the integer if found, else return -1.
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Q3. 
Count Subarrays with Sum Divisible by K
Given an array ARR and an integer K, your task is to count all subarrays whose sum is divisible by the given integer K.
Input:
The first line of input contains an...read more
Ans. 
Count subarrays with sum divisible by K in an array.
• Iterate through the array and keep track of the prefix sum modulo K.

• Use a hashmap to store the frequency of each prefix sum modulo K.

• For each prefix sum, increment the count by the frequency of (prefix sum - K) modulo K.

• Handle the case when prefix sum itself is divisible by K.

• Return the total count of subarrays with sum divisible by K.
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Round duration - 50 Minutes
Round difficulty - Medium

In this round , I was asked to code a simple question related to BST . After that I was asked the internal implementation of a Hash Map where I was supposed to design a Hash Map using any of the Hashing Algorithms that I know . This was preety challenging for me but I got to learn so much from it.

Q1. 
Ceil Value from BST Problem Statement
Given a Binary Search Tree (BST) and an integer, write a function to return the ceil value of a particular key in the BST.
The ceil of an integer is defined as the s...read more
Ans. 
Ceil value of a key in a Binary Search Tree (BST) is found by returning the smallest integer greater than or equal to the given number.
• Traverse the BST to find the closest value greater than or equal to the key.

• Compare the key with the current node value and update the ceil value accordingly.

• Recursively move to the left or right subtree based on the comparison.

• Return the ceil value once the traversal is complete.
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Q2. 
Design a Constant Time Data Structure
Create a data structure that maintains mappings between keys and values, supporting the following operations in constant time:
1. INSERT(key, value): Add or update t...read more
Ans. 
Design a constant time data structure to maintain mappings between keys and values with various operations.
• Use a hash table to achieve constant time complexity for INSERT, DELETE, SEARCH, and GET operations.

• Keep track of the number of key-value pairs for GET_SIZE operation.

• Check if the hash table is empty for IS_EMPTY operation.

• Return true or false for SEARCH operation based on key existence.

• Return the value associated...read more
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Round duration - 90 Minutes
Round difficulty - Hard

I found the online coding round of Flipkart to be quite difficult based on the constraints of the problem and their time limits. I coded the first problem quite easily but on the second and the third problem , my code could only pass a few test cases and gave TLE for most of them. Both the questions required very efficient solution and the last 5 to 10 Test Cases carried more weight than the rest so I didn't get through this round.

Q1. 
Print the Kth Digit
Given three non-negative integers N, M, and K, compute the Kth digit from the right in the number obtained from N raised to the power M (i.e., N ^ M).
Input:
The first line contains ...read more
Ans. 
The task is to find the Kth digit from the right in the number obtained from N raised to the power M.
• Iterate through the digits of N^M from right to left

• Keep track of the position of the current digit

• Return the digit at position K from the right
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Q2. 
The Skyline Problem
Compute the skyline of given rectangular buildings in a 2D city, eliminating hidden lines and forming the outer contour of the silhouette when viewed from a distance. Each building is ...read more
Ans. 
Compute the skyline of given rectangular buildings in a 2D city, eliminating hidden lines and forming the outer contour of the silhouette.
• Iterate through the buildings and create a list of critical points (x, y) where the height changes.

• Sort the critical points based on x-coordinate and process them to form the skyline.

• Merge consecutive horizontal segments of equal height into one to ensure no duplicates.

• Return the fin...read more
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Q3. 
Longest Palindromic Substring Problem Statement
You are provided with a string STR of length N. The goal is to identify the longest palindromic substring within this string. In cases where multiple palind...read more
Ans. 
Identify the longest palindromic substring in a given string.
• Iterate through the string and expand around each character to find palindromes

• Keep track of the longest palindrome found

• Return the longest palindrome with the smallest start index
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