DE Shaw Software Developer Interview Questions, Process, and Tips

Round duration - 120 Minutes
Round difficulty - Hard

Online Test Platform - HackerRank
Test Access Window – between 10:00 AM to 6:00 PM
Online Test Pattern –

Total Duration of Test – 120 mins
Total No. of Sections - 5
Section 1 – One Coding Question - Easy difficulty (20 mins)
Section 2 – One Coding Question - Medium difficulty (30 mins)
Section 3 – One Coding Question - Medium difficulty (30 mins)
Section 4 - Technical MCQs - 10 questions (20 mins)
Section 5 - Aptitude MCQs - 10 questions (20 mins)
Programming Sections (1, 2 and 3): This will have 3 coding questions with a time limit of 80 minutes. It is mandatory for you to attempt the 1st coding question before moving to the second question and third. You cannot revisit question/section once you proceed ahead
MCQ Sections (4 and 5): This will have 10 technical and 10 aptitude questions, with a time limit of 20 minutes each. Each correct answer will carry 2 marks and wrong answer will carry negative 0.5
Technical questions will cover Data structures & algorithms, Operating systems, Database systems, SQL and Networks.
Aptitude questions will cover Quantitative Aptitude, Problem solving and Logical & verbal Reasoning

Q1. 
Tower Building Problem Statement
Given an array 'ARR' of 'N' cubes, you need to construct towers such that each cube can either be placed on top of an existing tower or start a new one. The restriction is...read more
Ans. 
I stored the difference in heights.
Sorted this array
And filled the difference such that max length is observed.
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Q2. 
Minimum Removals Problem Statement
Given an array ARR of size N and an integer K, determine the minimum number of elements that must be removed from the array so that the difference between the maximum an...read more
Ans. Brute Force
We will first sort the given array. Then we will start traversing the array using two variables, say ‘i’ and ‘j,’ using a nested loop, where j will be used to fix the maximum element, and i will be used to fix the minimum element and check if arr[j] - arr[i] <= K.
 
Algorithm:
 
1. Sort the given array in increasing order.
2. Make an integer variable “answer” = N to store the minimum number of elements tha...read more
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Q3. 
Conquering the Best Kingdom Problem Statement
Aragorn, an influential ruler, aspires to expand his power by conquering more kingdoms. There are 'N' kingdoms numbered from 0 to N-1, forming a tree structur...read more
Ans. Greedy + Depth First Search
The question becomes easy if you are able to figure out that only the decision of selecting the first kingdom to conquer will be sufficient to determine the final answer. Let’s start with something more intuitive rather than directly jumping to the final answer. If you pick a random kingdom in your first turn, in subsequent turns both you and Aragorn you will greedily conquer all the kingdoms...read more
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Round duration - 60 Minutes
Round difficulty - Medium

They called and asked me to choose a date and time I would be free in the upcoming week for my interview.
I chose 10th March 5 pm. 

Interviewer was pretty friendly. Started with some resume based questions. Asked me OS, DBMS and JAVA based questions. A coding question was asked to code. Asked me OOPS related questions too.

Q1. 
K Most Frequent Elements Problem Statement
Given an integer array ARR and an integer K, identify the K most frequent elements within ARR. Return these elements sorted in ascending order.
Example:
Input:
...read more
Ans. QuickSelect
Prerequisite: Quick Sort
 
In this approach, we will try to divide the problem at every step into a smaller problem. We know that the kth top frequent element is (n - k)th less frequent. So, we will do a partial sort from the less frequent element to the most frequent one, till (n - k)th less frequent element takes place (n - k) in a sorted array. To do so, we will use quickselect. Quickselect is an algor...read more
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Round duration - 90 Minutes
Round difficulty - Medium

This round had 3 coding questions. The first two were of moderate level and the third one was a bit hard and was related to Dynamic Programming.

Q1. 
Maximum Number from Linked List Problem Statement
Given a linked list where each node contains a single digit, your task is to construct the largest possible number using these digits.
Objective:
Print ...read more
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Q2. 
Chocolate Distribution Problem
You are given an array/list CHOCOLATES of size 'N', where each element represents the number of chocolates in a packet. Your task is to distribute these chocolates among 'M'...read more
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Q3. 
LCS of Three Strings Problem Statement
Given three strings A, B, and C, determine the length of the longest common subsequence present in all three strings.
Explanation:
A subsequence is derived by dele...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round had 2 questions of DS/Algo to solve under 60 minutes and 2 questions related to Operating Systems.

Q1. 
Buy and Sell Stock Problem Statement
Imagine you are Harshad Mehta's friend, and you have been given the stock prices of a particular company for the next 'N' days. You can perform up to two buy-and-sell ...read more
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Q2. 
Count Smaller People on Right
You are provided with an array called HEIGHT that contains the heights of 'N' people standing in a queue. For each person in the array, compute the number of individuals on t...read more
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Q3. Can you define processes and threads in operating systems?
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Q4. What are the different types of semaphores?
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Round duration - 60 Minutes
Round difficulty - Medium

This round had 3 coding questions in which I first had to explain my approach with proper complexity analysis and then code up the solution. I found the first problem to be a bit on the harder side compared to the rest of the 2 problems.

Q1. 
Longest Increasing Path in a 2D Matrix Problem Statement
Given a matrix of non-negative integers of size 'N x M', where 'N' and 'M' denote the number of rows and columns respectively, find the length of t...read more
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Q2. 
Gas Station Tour Problem
You are presented with a circular track consisting of several petrol pumps. Each petrol pump is indexed from 0 to N-1 and offers certain attributes:
• The quantity of petrol ava...read more
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Q3. 
Rabbit Jumping Problem
Consider 'n' carrots numbered from 1 to 'n' and 'k' rabbits. Each rabbit jumps to carrots only at multiples of its respective jumping factor A_j (i.e., A_j, 2A_j, 3A_j, ...), for all ra...read more
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Round duration - 90 Minutes
Round difficulty - Hard

This round had 3 coding questions and the difficulty of the questions ranged from Moderate to Hard level.

Q1. 
Jump Game Problem Statement
You are given a list of points, and currently at point 0, your task is to determine if you can reach the last point N. At each point i, you can jump at most JUMP[i] length forw...read more
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Q2. 
Problem Statement: Sibling Nodes
You are provided with a Binary Tree consisting of 'N' nodes, where each node holds an integer value. Your objective is to identify and list all nodes that do not possess a...read more
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Q3. 
Minimum Steps for a Knight to Reach Target
Given a square chessboard of size 'N x N', determine the minimum number of moves a Knight requires to reach a specified target position from its initial position...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round went for about 50-60 minutes where I had to code two questions related to DSA after discussing their approaches and time and space complexities and then I was asked some questions revolving around OOPS. The interviewer was quite freindly and helped me at some places where I was facing some difficulties.

Q1. 
Evaluate Reverse Polish Notation Problem Statement
You are provided with an arithmetic expression in Reverse Polish Notation represented as an array EXP. Your task is to calculate the value of this expres...read more
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Q2. 
LCA in a Binary Search Tree
You are given a binary search tree (BST) containing N nodes. Additionally, you have references to two nodes, P and Q, within this BST.
Your task is to determine the Lowest Com...read more
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Q3. What is the Diamond Problem in C++ and how can it be resolved?
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Q4. What is meant by garbage collection in the context of Object-Oriented Programming (OOP)?
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Round duration - 60 Minutes
Round difficulty - Medium

This round consisted of two coding problems which involved proper coding it and explaining each and every aspect and showing the dry run over a few test cases was also necessary.

Q1. 
Phone Directory Search Directory
You are given a list/array of strings representing the contacts in a phone directory. The task is to perform a search based on a query string 'str' and return all contacts...read more
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Q2. 
Bottom View of Binary Tree
Given a binary tree, determine and return its bottom view when viewed from left to right. Assume that each child of a node is positioned at a 45-degree angle from its parent.
N...read more
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Round duration - 95 minutes
Round difficulty - Easy

This round was conducted in Hackerrank portal for a total duration of 95 minutes and was divided into 4 sections.

1st Section : Aptitude Section : 14 questions , 28 minutes
2nd Section : Technical Section : 12 questions , 17 minutes
3rd Section :1 coding Questions : 20 minutes+30 minutes

This Round was Conducted on Hackerrank (Webcam Enabled).

Q1. 
Coin Game Problem Statement
Wong wants to borrow money from Dr. Strange, who insists Wong must win a coin game first. The game involves two players taking turns to remove one coin from either end of a row...read more
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Q2. 
Find Magic Index in Sorted Array
Given a sorted array A consisting of N integers, your task is to find the magic index in the given array, where the magic index is defined as an index i such that A[i] = i...read more
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Round duration - 120 minutes
Round difficulty - Medium

This was an Online F2F Technical Round conducted on CodePair : Hackerrank. So, Basically You have to Run and Submit ( Pass All Test cases) in the Interview Round also (Like normal Coding Test) in Codepair : Hackerrank & along with that You should have to explain your Code and Approach to the Interviewers.
The Interviewers were helpful and didn't hesitate in giving hints. 
Timing - 10:00 A.M to 12:00 P.M

Q1. 
Minimum Number of Taps to Water the Garden
Given a garden that extends along a one-dimensional x-axis from point 0 to point N, your task is to determine the minimum number of taps needed to water the enti...read more
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Q2. 
Money Saving in Bank Problem
Harshit wants to save up money for his first car by depositing money daily in the Ninja bank with a specific increment strategy.
Starting with 1 rupee on the first Monday, th...read more
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Round duration - 120 minutes
Round difficulty - Hard

A lot of Variants based on Constraints were asked in this Round. They will ask you to write the final code for every question before Submitting it(run all test cases) so you won’t get any hints after running test cases in the IDE. ( So don’t Submit your code before dry running it on a lot of Test Cases on pen & paper , they allow to use pen & blank paper at the time of Interviews) .The Interviewers tried to trick in case of time complexities even if you gave the best one. So try to be confident.

Q1. 
Buy and Sell Stock Problem Statement
Imagine you are Harshad Mehta's friend, and you have been given the stock prices of a particular company for the next 'N' days. You can perform up to two buy-and-sell ...read more
Add your answer
Q2. 
Stock Investment Problem Statement
You are given the prices of a particular stock over 'N' consecutive days. Your task is to find the maximum profit that can be obtained by completing at most two transact...read more
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Round duration - 30 minutes
Round difficulty - Easy

This was a Telephonic Round (Audio Call). The HR was friendly and asked basic questions.
The timing was 2:00 PM to 2:30 PM.

Q1. 
Rabbit Jumping Problem
Consider 'n' carrots numbered from 1 to 'n' and 'k' rabbits. Each rabbit jumps to carrots only at multiples of its respective jumping factor A_j (i.e., A_j, 2A_j, 3A_j, ...), for all ra...read more
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Round duration - 45 minutes
Round difficulty - Medium

Technical Interview round with questions on Core Subjects mainly.

Q1. What is the difference between C and C++?
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Q2. What is a virtual function?
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Q3. What is inheritance in object-oriented programming?
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Q4. What is the difference between a Default Constructor and a Copy Constructor in Object-Oriented Programming?
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Round duration - 40 minutes
Round difficulty - Easy

Technical Interview round with questions on Core Subjects mainly.

Q1. What are the types of access modifiers in C++?
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Q2. What is the difference between DDL (Data Definition Language) and DML (Data Manipulation Language)?
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Q3. What are the key differences between a Primary Key and a Unique Key in a database management system?
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Q4. What is the difference between DBMS and RDBMS?
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Q5. What are the objectives of normalization in database management systems?
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Round duration - 30 minutes
Round difficulty - Easy

HR round with typical behavioral problems.

Round duration - 60 minutes
Round difficulty - Medium

Started with the discussion why do you want to join DE shaw. Since prior to my current company, I was working with a finance based company so they asked why do you want to come back to finance base company. So they asked my about debentures, bonds, mortgages and other financial jargons.
Then they asked questions related to DSA, OS etc.

Q1. 
Find Triplets with Given Sum Problem Statement
Given an array ARR consisting of N integers, your task is to identify all distinct triplets within the array that sum up to a given integer K.
Explanation:
...read more
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Q2. 
Minimum Number of Platforms Problem
Your task is to determine the minimum number of platforms required at a railway station so that no train has to wait.
Explanation:
Given two arrays:
• AT - represent...read more
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Q3. What is the difference between internal fragmentation and external fragmentation in operating systems?
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Q4. Write an SQL query to find the employee with the nth highest salary.
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Q5. How is Java platform independent?
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Q6. What is the difference between an abstract class and an interface in Java?
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