70+ Cognizant Interview Questions and Answers

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) while C does not.

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

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

Arrays have fixed size while dynamic arrays can resize themselves as needed.

• Arrays in Java have a fixed size that is specified when the array is created.

• Dynamic arrays in Java, like ArrayList, can resize themselves as needed to accommodate more elements.

• Example: int[] fixedArray = new int[5]; ArrayList<Integer> dynamicArray = new ArrayList<>();

Difference between compiler and interpreter with a coding challenge

• Compiler translates the entire code into machine language before execution while interpreter translates line by line during execution

• Compiler generates an executable file while interpreter does not

• Compiler is faster but debugging is harder while interpreter is slower but debugging is easier

• Coding challenge: Write a program to find the sum of two numbers and print the result

Switch case is used for multiple conditions while if else is for binary conditions. Sorting can be done using various algorithms.

• Switch case is faster than if else for multiple conditions

• If else is more readable for binary conditions

• Sorting can be done using bubble sort, insertion sort, quick sort, etc.

• Example code for bubble sort: for(i=0;iarr[j+1]){swap(&arr[j],&arr[j+1]);}}}

No, Kafka relies on ZooKeeper for cluster coordination and management.

• ZooKeeper is used for leader election, configuration management, and synchronization in Kafka clusters.

• Kafka brokers register themselves in ZooKeeper and use it to discover other brokers and partitions.

• Without ZooKeeper, Kafka cannot function as a distributed system.

• However, Kafka can be run in standalone mode without ZooKeeper for development and testing purposes.

Replications ensure fault tolerance and high availability of data in Kafka.

• Replications provide redundancy and ensure that data is not lost in case of node failures.

• They also improve read performance by allowing consumers to read from multiple replicas.

• Replications can be configured to have different levels of consistency guarantees.

• For example, a replication factor of 3 ensures that data is stored on 3 different nodes.

• If one node fails, the data can still be retrieved from t...read more

Pointers are variables that store memory addresses. Inheritance is a way to create new classes based on existing ones.

• Pointers allow direct access to memory locations, enabling efficient manipulation of data.

• In C++, pointers can be used to dynamically allocate memory.

• Inheritance allows for code reuse and the creation of more specialized classes.

• For example, a Car class can inherit from a Vehicle class, inheriting its properties and methods.

Program to sort list of numbers in C language

• Use sorting algorithms like bubble sort, selection sort, or insertion sort

• Implement the sorting logic in a function and call it in main function

• Ensure to handle edge cases like empty list or list with only one element

Use self join and delete to remove duplicate records in SQL

• Use a self join to identify duplicate records based on specific criteria

• Select the records to be deleted using the self join

• Use the DELETE statement to remove the duplicate records

A program using collections for archival process

• Use a collection like ArrayList or LinkedList to store the archival data

• Implement methods to add, remove, and retrieve data from the collection

• Consider using a HashMap or TreeMap for efficient searching and retrieval

• Use appropriate data structures and algorithms to optimize the archival process

Java is platform independent due to its bytecode and virtual machine architecture.

• Java code is compiled into bytecode, which can run on any platform with a Java Virtual Machine (JVM)

• JVM acts as an abstraction layer between the Java code and the underlying hardware

• This allows Java programs to be written once and run on any platform without modification

My favorite coding language is Python because of its readability, versatility, and extensive libraries.

• Python is known for its readability, making it easier to write and maintain code.

• Python is versatile and can be used for a wide range of applications, from web development to data analysis.

• Python has a vast collection of libraries that make it easy to implement complex functionalities without reinventing the wheel.

Microservice is a software architecture pattern where an application is built as a collection of small, independent services.

• Microservices are independently deployable and scalable.

• Each microservice performs a specific business function.

• Communication between microservices is usually done through APIs.

• Microservices can be written in different programming languages and use different data storage technologies.

• Examples of companies using microservices include Netflix, Amazon, and...read more

Scope defines the visibility of variables, transient is short-lived, and singleton is a single instance shared across the application.

• Scope determines the visibility and lifetime of variables in a program.

• Transient objects are short-lived and are typically used for temporary data storage.

• Singleton pattern ensures a class has only one instance and provides a global point of access to it.

A Consumer Group is a group of consumers that collectively consume messages from one or more topics.

• Consumer Groups allow for parallel processing of messages from a topic

• Each consumer group maintains its own offset for each partition of a topic

• Multiple consumer groups can consume messages from the same topic

• Consumer Groups are commonly used in Apache Kafka

Web services are software systems designed to support interoperable machine-to-machine interaction over a network.

• Web services allow different applications to communicate with each other over the internet.

• They use standardized protocols like HTTP, XML, SOAP, and REST.

• Web services can be used for a variety of purposes, such as sharing data between different systems or integrating different applications.

• Examples of web services include Google Maps API, Amazon Web Services, and ...read more

staticmethod and class method are two types of methods in Python classes.

• staticmethod is a method that belongs to a class but does not have access to the class or instance.

• classmethod is a method that belongs to a class and has access to the class but not the instance.

• staticmethod is used when a method does not need to access the class or instance.

• classmethod is used when a method needs to access the class but not the instance.

• Example of staticmethod: @staticmethod def method...read more

An array is a data structure that stores a collection of elements of the same type in a contiguous memory location.

• Arrays have a fixed size determined at the time of declaration.

• Elements in an array are accessed using an index starting from 0.

• Example: string[] names = {"Alice", "Bob", "Charlie"};

Neural networks are a type of machine learning algorithm inspired by the human brain, used for pattern recognition and prediction.

• Neural networks consist of layers of interconnected nodes that process input data and produce output.

• They are trained using labeled data to learn patterns and relationships in the data.

• Common types include feedforward neural networks, convolutional neural networks, and recurrent neural networks.

• Examples of neural network applications include image ...read more

OOPS concepts are fundamental principles in object-oriented programming that help in organizing and designing code efficiently.

• Encapsulation: Bundling data and methods that operate on the data into a single unit. Example: a car object with properties like color and methods like start() and stop().

• Inheritance: Allowing a class to inherit properties and behavior from another class. Example: a class Animal with subclasses like Dog and Cat inheriting common attributes like name a...read more

OOP concept in Java refers to the principles of Object-Oriented Programming that allow for modular and reusable code.

• Encapsulation: bundling data and methods together in a class

• Inheritance: creating new classes from existing ones

• Polymorphism: using a single interface to represent different types

• Abstraction: hiding complex implementation details

• Example: Creating a class 'Car' with properties like 'color' and methods like 'startEngine'

Props in React js are used to pass data from parent to child components.

• Props are read-only and cannot be modified by the child component.

• Props are passed down from parent to child components using attributes.

• Props help in creating reusable components by passing dynamic data.

• Example:

Data structures are ways to organize and store data in a computer so that it can be accessed and manipulated efficiently.

• Examples include arrays, linked lists, stacks, queues, trees, graphs, hash tables, and heaps.

• Arrays store elements of the same data type in contiguous memory locations.

• Linked lists consist of nodes where each node contains a data field and a reference to the next node.

• Stacks follow the Last In First Out (LIFO) principle, while queues follow the First In Fir...read more

OOPs concepts refer to Object-Oriented Programming principles such as inheritance, encapsulation, polymorphism, and abstraction.

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

• Encapsulation: Bundling data and methods that operate on the data into a single unit.

• Polymorphism: Ability to present the same interface for different data types.

• Abstraction: Hiding the complex implementation details and showing only the necessary features.

Some new features in .NET Core include cross-platform support, performance improvements, and modular design.

• Cross-platform support allows developers to build and run applications on Windows, macOS, and Linux.

• Performance improvements such as faster startup times and lower memory usage.

• Modular design with smaller runtime packages for more efficient deployment.

• Support for C# 8.0 features like nullable reference types and async streams.

Code to reverse an array of strings.

• Create a new array to store the reversed strings.

• Iterate through the original array in reverse order and add each element to the new array.

• Return the new array as the reversed array.

I have used 'django.db.models' package in my Django models.

• The 'django.db.models' package provides the base classes for defining models in Django.

• It includes classes like 'Model', 'CharField', 'IntegerField', 'ForeignKey', etc.

• These classes are used to define the fields and relationships in a Django model.

• For example, 'class MyModel(models.Model): name = models.CharField(max_length=50)'

• This creates a model with a 'name' field that is a character field with a maximum length of...read more

Sorting and searching techniques in Java

• Sorting techniques: Bubble sort, Selection sort, Insertion sort, Merge sort, Quick sort

• Searching techniques: Linear search, Binary search

• Example: Sorting an array of strings using merge sort

• Example: Searching for a specific string using binary search

State in React js is a JavaScript object that stores data and determines how a component renders and behaves.

• State is mutable and can be updated using the setState() method

• State is local to a component and can be passed down to child components as props

• State should be used for data that will change over time within a component

Denormalization is the process of adding redundant data to a database to improve read performance.

• Reduces the need for joins, improving query performance

• Increases data redundancy but can improve read performance

• Commonly used in data warehousing and reporting applications

Dependency injection is a design pattern in which components are given their dependencies rather than creating them internally.

• Allows for easier testing by mocking dependencies

• Promotes loose coupling between components

• Improves code reusability and maintainability

• Examples: Constructor injection, Setter injection, Interface injection

The static keyword in programming is used to declare variables, methods, or classes that belong to the class itself rather than instances of the class.

• Static variables are shared among all instances of a class.

• Static methods can be called without creating an instance of the class.

• Static classes cannot be instantiated and are used for grouping related methods and variables.

• Example: public static int count = 0; // static variable

OOPs concepts are used in real-world projects to organize code into classes and objects for better structure and reusability.

• Encapsulation: Grouping data and methods into a single unit to protect data from outside interference. Example: Creating a class 'Car' with private variables like 'model' and 'year' and public methods to access and modify them.

• Inheritance: Creating new classes based on existing ones to reuse code and extend functionality. Example: Creating a class 'SUV'...read more

ZooKeeper is a distributed coordination service for managing configuration, synchronization, and naming.

• ZooKeeper provides a hierarchical namespace for distributed systems.

• It is used for maintaining configuration information, naming, providing distributed synchronization, and group services.

• ZooKeeper is used in Apache Hadoop, Apache Kafka, and Apache Storm.

• It uses a consensus protocol called ZAB (ZooKeeper Atomic Broadcast) to maintain consistency and order among servers.

A diode is a semiconductor device that allows current to flow in one direction only.

• Diodes have two terminals - an anode and a cathode.

• When a positive voltage is applied to the anode and a negative voltage to the cathode, the diode conducts current.

• Reverse biasing the diode blocks current flow.

• Common types of diodes include rectifier diodes, zener diodes, and light-emitting diodes (LEDs).

Different datatypes refer to the various categories of data that can be stored and manipulated in a programming language.

• Datatypes include integers, floating point numbers, strings, booleans, arrays, and objects.

• Examples: int x = 5; float y = 3.14; string name = 'John'; bool isTrue = true; array numbers = [1, 2, 3]; object person = {name: 'Alice', age: 25};

Sorting is the process of arranging items in a specific order, typically in ascending or descending order.

• Sorting helps in organizing data for easier retrieval and analysis.

• Common sorting algorithms include bubble sort, merge sort, and quick sort.

• Example: Sorting a list of numbers in ascending order: [5, 2, 8, 1] -> [1, 2, 5, 8]

OOP 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.

• OOP focuses on creating objects that interact with each other to solve problems.

• Key concepts include classes, objects, inheritance, polymorphism, and encapsulation.

• Classes are blueprints for creating objects, defining their properties and behaviors.

• Objects are instances of classes, representing real-world entities.

• Inheritance allows cl...read more

I expect a challenging work environment, opportunities for growth, and a supportive team.

• Challenging work that allows me to utilize my skills and learn new technologies

• Opportunities for career advancement and professional development

• A supportive team that encourages collaboration and innovation

The project code is a web application for managing tasks and deadlines.

• Use HTML, CSS, and JavaScript for front-end development

• Use Node.js and Express for back-end development

• Implement CRUD operations for tasks and deadlines

• Utilize MongoDB for database storage

Window function is a function that performs a calculation across a set of rows in a table.

• Window functions are used to calculate values based on a specific window or subset of rows.

• They allow for calculations that involve multiple rows without the need for self-joins or subqueries.

• Common window functions include ROW_NUMBER, RANK, and SUM.

• Example: calculating the average salary for each department using the AVG window function.

Indexes are data structures used to improve the speed of data retrieval operations in databases.

• Indexes are created on columns in database tables to quickly locate rows based on the values in those columns.

• They help in reducing the number of disk I/O operations required when querying data.

• Examples include primary keys, unique keys, and indexes created on frequently searched columns.

Use the pandas library to extract multiple columns from a DataFrame

• Use the loc or iloc method to select specific columns by their index or label

• Specify the columns you want to extract within the square brackets

• Use double square brackets to return a DataFrame with the selected columns

I have worked on projects involving web development using technologies such as JavaScript, React, Node.js, and MongoDB.

• Web development projects

• JavaScript

• React

• Node.js

• MongoDB

Sorting in a dictionary

• Use sorted() function to sort the dictionary by keys or values

• Use lambda function to sort the dictionary by custom key

• Use OrderedDict() to maintain the order of the sorted dictionary

Machine learning types include supervised learning, unsupervised learning, and reinforcement learning.

• Supervised learning: Uses labeled data to train a model to make predictions (e.g. classification, regression)

• Unsupervised learning: Finds patterns in data without labeled outcomes (e.g. clustering, dimensionality reduction)

• Reinforcement learning: Learns through trial and error by receiving feedback from the environment (e.g. game playing, robotics)

Clean code is well-structured, readable, and maintainable code that follows best practices and standards.

• Clean code is easy to read and understand by others.

• It follows consistent naming conventions for variables, functions, and classes.

• Clean code is modular, with each function or class having a single responsibility.

• It minimizes duplication and follows the DRY (Don't Repeat Yourself) principle.

• Clean code is well-tested and documented for easier maintenance.

Dataframe is a data structure used in programming for storing and analyzing data in rows and columns.

• Dataframe is commonly used in libraries like Pandas in Python for data manipulation and analysis.

• It is similar to a table in a relational database, with rows representing observations and columns representing variables.

• Dataframes can be easily filtered, sorted, and transformed to extract insights from the data.

• Example: In Pandas, you can create a dataframe from a dictionary or...read more

C is a procedural programming language while C++ is an object-oriented programming language.

• C is a subset of C++.

• C does not support classes and objects, while C++ does.

• C++ supports function overloading and operator overloading, which C does not.

• C++ has a more complex syntax compared to C.

• C++ has a standard template library (STL) for data structures and algorithms, which C does not have.

Printing a specific pattern using loops in Java

• Use nested loops to print the desired pattern

• Start with the outer loop for rows and inner loop for columns

• Adjust the loop conditions to print the pattern correctly

Functional interface is an interface with only one abstract method, used in Java to achieve functional programming.

• Functional interface can have multiple default or static methods but only one abstract method.

• It can be used to implement lambda expressions in Java.

• Examples of functional interfaces in Java include Runnable, Callable, and ActionListener.

CRUD operations in MVC refer to Create, Read, Update, and Delete operations for interacting with data in a database.

• Create - Adding new data to the database

• Read - Retrieving existing data from the database

• Update - Modifying existing data in the database

• Delete - Removing data from the database

MVC life cycle involves request handling, routing, controller execution, view rendering, and response generation.

• Request is received by the router

• Router maps the request to the appropriate controller

• Controller processes the request and interacts with the model

• Model updates the data and sends it back to the controller

• Controller passes data to the view for rendering

• View generates the response and sends it back to the client

Use C# to reverse a given phrase

• Use the built-in method Reverse() to reverse a string

• Convert the string to a char array, reverse it, then convert it back to a string

• Iterate through the string and build a new string in reverse order

I am a software developer with 5 years of experience in Java and Python.

• Experienced software developer

• Proficient in Java and Python

• 5 years of industry experience

Singleton design pattern ensures a class has only one instance and provides a global point of access to it.

• Ensures a class has only one instance

• Provides a global point of access to that instance

• Commonly used in scenarios where only one instance of a class is needed, such as database connections or logging