DE Shaw Software Engineer Interview Questions and Answers

Q1. Easy array problem
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Q2. Easy tree traversal problem
Ans. 
Implement tree traversal algorithm to visit each node in a tree structure
• Use depth-first search (DFS) or breadth-first search (BFS) to traverse the tree

• DFS can be implemented using recursion or a stack data structure

• BFS can be implemented using a queue data structure

• Example: Inorder traversal of a binary tree - left, root, right
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Q1. Trapping rain water
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Q2. Path of longest sum
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Find the path in a matrix with the longest sum of elements
• Start from the top-left corner of the matrix

• Move only right or down in the matrix

• Keep track of the sum of elements in each path

• Return the path with the longest sum
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Q1. Explain OOPS concept and how you apply it in your implementation
Ans. 
OOPS is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.
• OOPS focuses on the concept of classes and objects

• Encapsulation: bundling data and methods that operate on the data within a single unit

• Inheritance: allows a class to inherit properties and behavior from another class

• Polymorphism: ability to present the same interface for diffe...read more
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Q2. Difference between Comparable and Comparator. Difference between Abstract Class and Interface
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Comparable is an interface used for natural ordering, Comparator is an interface used for custom ordering. Abstract class can have method implementations, Interface cannot.
• Comparable interface is used to define the natural ordering of objects. Example: String class implements Comparable interface for natural ordering based on alphabetical order.

• Comparator interface is used to define custom ordering of objects. Example:...read more
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Q3. Given a string. Find the number of occurrences of each character
Ans. 
Count occurrences of each character in a given string
• Create an array to store the count of each character

• Iterate through the string and increment the count of each character in the array

• Return the array with counts for each character
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Q4. Given an array. Remove the number of duplicates
Ans. 
Remove duplicates from an array of strings
• Iterate through the array and store each element in a set to keep track of unique values

• Create a new array with the unique values from the set
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Q5. Given a student object having name and grade data variables. Sort the object on the basis of highest grade.
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Q1. Discuss the project you are most proud of
Ans. 
Developed a mobile app for tracking personal fitness goals
• Used React Native to create a cross-platform app

• Implemented features such as goal setting, progress tracking, and workout logging

• Integrated with wearable devices like Fitbit for automatic data syncing
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Q2. What are ways to speed up SQL queries? List them in increasing order of complexity?
Ans. 
Ways to speed up SQL queries in increasing order of complexity
• Use indexes on columns frequently used in WHERE clauses

• Optimize queries by avoiding unnecessary joins and subqueries

• Use stored procedures to reduce network traffic and improve performance

• Consider denormalizing tables for frequently accessed data

• Use query optimization techniques like query caching and query hints
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Q3. Is Redis single-threaded or multi-threaded?
Ans. 
Redis is single-threaded.
• Redis is single-threaded, meaning it can only execute one command at a time.

• This design choice allows Redis to be extremely fast and efficient for certain use cases.

• However, it also means that Redis may not be the best choice for highly concurrent workloads.
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Q4. What sort of data types can be used as keys in Python?
Ans. 
Data types that can be used as keys in Python include strings, integers, floats, tuples, and custom objects.
• Strings are commonly used as keys in Python dictionaries.

• Integers and floats can also be used as keys.

• Tuples can be used as keys if they only contain immutable elements.

• Custom objects can be used as keys if they are hashable.

• Examples: {'name': 'John'}, {1: 'apple'}, {(1, 2): 'tuple'}
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Q5. What types of indexing exist in SQL?
Ans. 
Types of indexing in SQL include clustered, non-clustered, unique, and composite indexes.
• Clustered index physically reorders the table based on the index key

• Non-clustered index creates a separate structure for the index

• Unique index ensures that all values in the index column are unique

• Composite index uses multiple columns for indexing
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Q1. Basic java fundamentals
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Q2. Spring boot,sql
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Q1. Some technical questions from manager
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Q2. Some challenges or scenario based questions
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Q1. Salary discussion mostly
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Q2. Benifts that they offer with TR
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The coding test consists of multiple-choice questions and one medium-hard level coding question.

Q1. Given three jugs with different capacities and no measuring tools, how can you measure out a specific amount of water using the jugs you have?
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Q2. What is the angle between the minute and hour hand of a clock at 3:45?
Ans. 
The angle between the minute and hour hand of a clock at 3:45 is 157.5 degrees.
• Calculate the angle formed by the hour hand from 12 o'clock position to 3:45 position (135 degrees)

• Calculate the angle formed by the minute hand from 12 o'clock position to 3:45 position (22.5 degrees)

• Subtract the smaller angle from the larger angle to get the angle between the two hands (157.5 degrees)
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Q3. What is indexing in Database Management Systems (DBMS)?
Ans. 
Indexing in DBMS is a technique used to improve the performance of queries by allowing faster retrieval of data.
• Indexes are data structures that store a small portion of the data set in an easily searchable format.

• They help in speeding up the data retrieval process by reducing the number of disk accesses needed.

• Indexes can be created on one or more columns of a table to improve the performance of SELECT queries.

• Example...read more
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Q4. What is the lifecycle of a React component?
Ans. 
The lifecycle of a React component includes mounting, updating, and unmounting phases.
• Mounting phase: constructor, render, componentDidMount

• Updating phase: shouldComponentUpdate, render, componentDidUpdate

• Unmounting phase: componentWillUnmount
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Q5. How you delete entry in mongodb database
Ans. 
To delete an entry in MongoDB database, you can use the deleteOne() or deleteMany() methods.
• Use deleteOne() method to delete a single document based on a specific condition

• Use deleteMany() method to delete multiple documents based on a specific condition

• Make sure to specify the filter criteria to accurately delete the desired entry
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