DE Shaw Software Developer Interview Questions, Process, and Tips

To find the maximum length BST in a given binary tree.

• Traverse the tree in post-order fashion

• For each node, check if it satisfies the BST property

• If it does, calculate the size of the BST rooted at that node

• Keep track of the maximum size seen so far

Algorithm to find absolute max subsequence of an array with positive and negative numbers in O(n) time.

• Initialize max_so_far and max_ending_here as 0

• Loop through the array and for each element, add it to max_ending_here

• If max_ending_here becomes negative, reset it to 0

• If max_ending_here is greater than max_so_far, update max_so_far

• Return max_so_far

Eliminate duplicates in an array of strings and print it in linear time complexity.

• Use a hash set to keep track of unique elements

• Iterate through the array and add non-duplicate elements to the hash set

• Print the hash set elements to get the final array

Balancing of Btrees / AVL trees is important for efficient search and insertion operations.

• Btrees and AVL trees are self-balancing binary search trees.

• Balancing ensures that the height of the tree is minimized, leading to faster search and insertion operations.

• Btrees are used in databases while AVL trees are used in memory.

• Balancing is achieved by performing rotations and node splitting.

• AVL trees have a stricter balanc...read more

139 teams in a knock-out tournament, find the number of matches to choose the champion.

• In a knock-out tournament, each team plays only one match per round.

• The number of matches required to choose the champion is one less than the number of teams.

• Therefore, the number of matches required is 138.

My resume includes projects such as a web-based inventory management system and a mobile app for tracking fitness goals.

• Developed a web-based inventory management system using PHP and MySQL

• Created a mobile app for tracking fitness goals using React Native

• Implemented RESTful APIs for communication between front-end and back-end

• Utilized version control tools such as Git for collaborative development

• Designed and implement...read more

Algorithm to mirror a given Binary Tree

• Create a function to swap left and right child nodes of a given node

• Recursively call the function on left and right child nodes

• Base case: if node is null, return

• Call the function on the root node of the binary tree

Find the next largest int with same number of 1's in binary.

• Count the number of 1's in the binary representation of the given int.

• Increment the given int until a number with the same number of 1's is found.

• Return the next largest int with same number of 1's.

OOP concepts in Java

• Encapsulation - hiding implementation details

• Inheritance - creating new classes from existing ones

• Polymorphism - ability of objects to take on multiple forms

• Abstraction - focusing on essential features and ignoring the rest

• Example: A Car class can inherit from a Vehicle class

• Example: A Dog class can have a bark() method that overrides the Animal class's makeSound() method

• Example: A Shape class can h...read more

Answering OOP Java design problems

• Identify the problem domain and create a class hierarchy

• Use encapsulation to hide implementation details

• Apply inheritance to reuse code and create subtypes

• Implement polymorphism to allow objects to take on multiple forms

• Avoid tight coupling and favor composition over inheritance

• Use design patterns to solve common problems

• Consider SOLID principles for maintainable code

C++ is an extension of C with object-oriented programming features.

• C++ supports classes and objects while C does not.

• C++ has better support for polymorphism and inheritance.

• C++ has a standard template library (STL) which C does not have.

• C++ allows function overloading while C does not.

• C++ has exception handling while C does not.

Inheritance is a mechanism in object-oriented programming where a new class is created by inheriting properties of an existing class.

• Inheritance allows code reusability and saves time and effort in programming.

• The existing class is called the superclass or parent class, and the new class is called the subclass or child class.

• The subclass inherits all the properties and methods of the superclass and can also add its own...read more

Default constructor is provided by the compiler if no constructor is defined. Copy constructor creates a new object by copying an existing object.

• Default constructor initializes member variables to default values.

• Copy constructor creates a new object with the same values as an existing object.

• Default constructor is called automatically by the compiler if no constructor is defined.

• Copy constructor is called when an obje...read more

Access specifiers are keywords in object-oriented programming languages that determine the visibility and accessibility of class members.

• Access specifiers are used to restrict access to class members.

• There are three types of access specifiers: public, private, and protected.

• Public members can be accessed from anywhere in the program.

• Private members can only be accessed within the class.

• Protected members can be accessed...read more

Library functions are pre-written code that can be reused to perform common tasks.

• Library functions save time and effort by providing pre-written code.

• They are often included in programming languages or external libraries.

• Examples include functions for string manipulation, mathematical calculations, and file input/output.

• Library functions can be called from within a program to perform specific tasks.

• They can also be cu

DML is Data Manipulation Language used to manipulate data in a database. DLL is Data Definition Language used to define database schema.

• DML is used to insert, update, delete data in a database.

• DLL is used to create, alter, drop database objects like tables, views, indexes.

• DML statements include INSERT, UPDATE, DELETE.

• DLL statements include CREATE, ALTER, DROP.

• DML affects data in a database, DLL affects the structure of

Primary key uniquely identifies a record in a table, while unique key ensures that all values in a column are distinct.

• Primary key can't have null values, while unique key can have one null value.

• A table can have only one primary key, but multiple unique keys.

• Primary key is used as a foreign key in other tables, while unique key is not.

• Example: Primary key - employee ID, Unique key - email address.

A stack is a data structure that follows the Last-In-First-Out (LIFO) principle.

• Elements are added to the top of the stack and removed from the top.

• Common operations include push (add element) and pop (remove element).

• Stacks can be implemented using arrays or linked lists.

• Examples include the call stack in programming and the undo/redo feature in text editors.

Assembly is a low-level programming language that is used to write programs that can directly interact with computer hardware.

• Assembly language is specific to a particular computer architecture.

• It is a low-level language that is difficult to read and write.

• Assembly language programs are faster and more efficient than programs written in high-level languages.

• Examples of assembly language include x86, ARM, and MIPS.

• Assem...read more

Class access modifiers are keywords used to control the visibility and accessibility of class members.

• There are four access modifiers in Java: public, private, protected, and default

• Public members can be accessed from anywhere

• Private members can only be accessed within the same class

• Protected members can be accessed within the same class, subclasses, and same package

• Default members can be accessed within the same packa

Serialization is the process of converting an object into a format that can be stored or transmitted.

• Serialization is used to save the state of an object and recreate it later.

• It is commonly used in network communication to transmit data between different systems.

• Examples of serialization formats include JSON, XML, and binary formats like Protocol Buffers.

• Deserialization is the opposite process of converting serialized

Normalisation is the process of organizing data in a database to reduce redundancy and improve data integrity.

• Normalisation helps to eliminate data redundancy and inconsistencies

• It ensures that each piece of data is stored in only one place

• It helps to improve data integrity and accuracy

• It makes it easier to maintain and update the database

• There are different levels of normalisation, each with its own set of rules and g

Truncate removes all data from a table while Delete removes specific data from a table.

• Truncate is faster than Delete as it doesn't log individual row deletions.

• Truncate resets the identity of the table while Delete doesn't.

• Truncate can't be rolled back while Delete can be.

• Truncate doesn't fire triggers while Delete does.

DBMS is a software system to manage databases while RDBMS is a type of DBMS that uses a relational model.

• DBMS stands for Database Management System while RDBMS stands for Relational Database Management System.

• DBMS can manage any type of database while RDBMS uses a relational model to manage data.

• DBMS does not enforce any specific data model while RDBMS enforces a relational data model.

• Examples of DBMS include MongoDB, ...read more

Recursion function is a function that calls itself until a base condition is met.

• Recursion is a technique used to solve problems by breaking them down into smaller sub-problems.

• It involves a function calling itself with a modified input until a base case is reached.

• Recursion can be used to solve problems such as factorial, Fibonacci series, and binary search.

• Recursion can be implemented using loops as well, but it may ...read more