100+ Wissen Technology Interview Questions and Answers

Remove duplicates from array of strings

• Create a Set to store unique strings

• Iterate through the array and add each string to the Set

• Convert the Set back to an array to get the unique strings

Find the maximum sum of a contiguous subarray within an array of integers.

• Use Kadane's algorithm to find the maximum sum subarray efficiently.

• Iterate through the array and keep track of the maximum sum ending at each index.

• Reset the sum to 0 if it becomes negative, as a negative sum will never contribute to the maximum sum.

HashMap is a data structure that stores key-value pairs and uses hashing to quickly retrieve values based on keys.

• HashMap internally uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to determine the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• To retrieve a value, the key is hashed again to find the index and then the linked list is searche...read more

React JS is a JavaScript library for building user interfaces.

• React JS is maintained by Facebook.

• It allows developers to create reusable UI components.

• React JS uses a virtual DOM for better performance.

• Current stable version is 17.0.2 (as of September 2021).

A program to find the next palindrome number after a given number.

• Convert the given number to a string to easily manipulate individual digits.

• Increment the number by 1 and check if it is a palindrome.

• If not a palindrome, repeat the process until a palindrome is found.

Use a custom comparator function to sort the deck of cards based on their rank and suit.

• Create a custom comparator function that compares the rank and suit of two cards.

• Use the custom comparator function to sort the deck of cards.

• Example: ['2H', '3D', 'AS', ...]

Vlookup is a function in Excel used to search for a value in a table and return a corresponding value.

• Vlookup stands for 'Vertical Lookup'

• It is commonly used in Excel to search for a value in the leftmost column of a table and return a value in the same row from a specified column

• For example, =VLOOKUP(100, A1:B10, 2, FALSE) would search for the value 100 in column A and return the corresponding value in column B

Lifecycle hooks in Angular are methods that allow you to tap into the lifecycle of a component or directive.

• Lifecycle hooks include ngOnInit, ngOnChanges, ngDoCheck, ngOnDestroy, etc.

• ngOnInit is used to initialize data in a component after Angular has initialized the component.

• ngOnChanges is called when the input properties of a component change.

• ngDoCheck is used for detecting and acting on changes that Angular doesn't detect on its own.

• ngOnDestroy is called just before the d...read more

The question is about finding anagrams in a given string.

• An anagram is a word or phrase formed by rearranging the letters of another word or phrase.

• To find anagrams in a string, we can use a hashmap to store the frequency of characters in each word.

• We can iterate through the string and for each substring of length equal to the length of the target word, check if it is an anagram.

• If the frequency of characters in the substring matches the frequency of characters in the target ...read more

Xpath for Google search button

• Use the following Xpath: //input[@name='btnK']

• The 'btnK' is the name attribute of the Google search button

• Make sure to test the Xpath in a browser console to ensure accuracy

Implicit and Explicit waits are used in Selenium to handle synchronization issues in web automation testing.

• Implicit wait is used to tell the WebDriver to wait for a certain amount of time before throwing a NoSuchElementException.

• Explicit wait is used to tell the WebDriver to wait for a certain condition to occur before proceeding further.

• Implicit wait is set globally for the entire WebDriver instance, while explicit wait is applied only to specific elements.

• Example: driver.m...read more

Split array into subarrays of specified size

• Use a loop to iterate through the array and slice it based on the split size

• Check if the remaining elements are less than the split size and handle them accordingly

• Return the array of subarrays

Collection is a single interface in Java while Collections is a utility class containing static methods for operating on collections.

• Collection is an interface in Java that represents a group of objects known as elements. It is a single entity.

• Collections is a utility class in Java that contains static methods for operating on collections like sorting, searching, etc.

• Example: List is a Collection interface while Collections.sort() is a static method in the Collections class.

Status code 302 is a temporary redirect response status code indicating that the requested resource has been temporarily moved to a different URL.

• 302 Found is commonly used in response to a POST/PUT/DELETE request to indicate that the resource has been temporarily moved to a different URL.

• It is often used during website maintenance or when a webpage has been moved to a new location temporarily.

• The client should continue to use the original URL for future requests as the redir...read more

oob (out-of-bag) is a validation method used in random forest where each decision tree is trained using a subset of data and tested on the remaining data.

• oob error is calculated by averaging the error for each observation that is not used in training the decision tree.

• oob error provides an unbiased estimate of the model's performance without the need for a separate validation set.

• oob error can be used to tune hyperparameters and assess the effectiveness of the random forest m...read more

Develop a chat app for real-time communication

• Use WebSocket for real-time communication

• Implement user authentication and authorization

• Design a user-friendly interface with features like emojis and file sharing

Object-oriented programming is a programming paradigm based on the concept of objects, which can contain data and code.

• Features of OOP include encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation allows objects to hide their internal state and require all interaction to be performed through an object's methods.

• Inheritance allows classes to inherit attributes and methods from other classes.

• Polymorphism allows objects to be treated as instances of their paren...read more

Netflix is a streaming service that offers a wide variety of TV shows, movies, anime, documentaries, and more on thousands of internet-connected devices.

• Netflix operates on a subscription-based model where users pay a monthly fee to access content.

• Users can stream content on various devices such as smart TVs, smartphones, tablets, and computers.

• Netflix uses algorithms to recommend content based on users' viewing history and preferences.

• The platform also produces original cont...read more

Partitioning in Hive is a way to organize data in a table into multiple partitions based on one or more keys.

• Partitioning helps in improving query performance by allowing Hive to only read the relevant partitions instead of scanning the entire table.

• Partitions can be based on one or more columns, such as date, region, or category.

• Partitioning can also help in managing large datasets efficiently by dividing them into smaller, manageable chunks.

• Example: Partitioning a sales tab...read more

Find the maximum sum of a subarray of size k in an array of integers.

• Use a sliding window approach to keep track of the sum of the current subarray.

• Slide the window by adding the next element and subtracting the previous element.

• Keep track of the maximum sum encountered so far.

• Return the maximum sum found.

Find the longest common prefix among an array of strings.

• Iterate through the characters of the first string and compare with other strings.

• Stop when a character doesn't match or reach the end of any string.

• Return the prefix found so far.

In software testing, 'throw' is used to raise an exception, while 'throws' is used to declare exceptions that a method may throw.

• throw is used to raise an exception in a program

• throws is used in method signature to declare exceptions that the method may throw

• throw is a keyword in Java, while throws is a keyword used in method declaration

Microservices are a architectural style that structures an application as a collection of loosely coupled services, while APIs are interfaces that allow different software systems to communicate with each other.

• Microservices are independent, self-contained services that can be developed, deployed, and scaled independently.

• APIs are interfaces that define how different software components should interact with each other.

• Microservices communicate with each other through APIs, wh...read more

BRD is a high-level document that outlines business requirements. FSD is a detailed document that specifies functional requirements.

• BRD focuses on business needs and goals, while FSD focuses on how the system will meet those needs.

• BRD is usually created by business analysts, while FSD is created by developers and technical teams.

• BRD is less technical and more focused on the big picture, while FSD is highly technical and detailed.

• Example: BRD may state the need for a customer ...read more

BRD and FSD are documents used in software development to define requirements and specifications.

• BRD stands for Business Requirements Document and outlines the business needs and objectives for a project.

• FSD stands for Functional Specification Document and details the technical requirements and specifications for a project.

• BRD focuses on the business perspective while FSD focuses on the technical perspective.

• Both documents are used to ensure that the final product meets the c...read more

Apex asynchronous batch is used for processing large data sets asynchronously.

• Batch Apex is used for processing large data sets asynchronously

• It is used to avoid governor limits and timeouts

• Batch Apex can be scheduled to run at a specific time or can be executed manually

• Example: Updating all accounts with a specific field value using Batch Apex

Trade cycle refers to the fluctuations in economic activity that occur over time, including periods of expansion and contraction.

• Trade cycle consists of four phases: expansion, peak, contraction, and trough.

• During expansion, there is an increase in economic activity, such as rising GDP and employment.

• The peak is the highest point of economic activity before a downturn begins.

• Contraction involves a decrease in economic activity, leading to lower GDP and increased unemployment....read more

Microservices are a software architecture design where applications are broken down into smaller, independent services that communicate with each other through APIs.

• Microservices allow for greater flexibility and scalability in software development.

• Each microservice is responsible for a specific function or feature of the application.

• Microservices can be developed, deployed, and scaled independently of each other.

• They communicate with each other through APIs, often using ligh...read more

Design classes for different features of Facebook platform

• Create a User class with attributes like name, email, password, friends list

• Create a Post class with attributes like content, likes, comments, timestamp

• Create a Comment class with attributes like content, user, timestamp

• Create a Like class with attributes like user, post

• Consider inheritance for classes like PhotoPost, VideoPost, etc.

Design a parking lot system for efficient management of parking spaces.

• Use object-oriented design principles to create classes for parking lot, parking space, vehicle, etc.

• Implement algorithms for efficient parking space allocation and retrieval.

• Incorporate features like ticketing system, payment processing, and monitoring.

• Consider scalability and performance optimization for handling a large number of vehicles.

• Include a user-friendly interface for drivers to easily navigate ...read more

OOPS concept refers to Object-Oriented Programming principles like 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.

Solving a pseudo code problem in an interview for Junior Engineer - Quality Assurance

• Understand the logic of the pseudo code provided

• Identify the variables and operations being performed

• Write the code in a programming language of your choice to solve the problem

• Test the code with different inputs to ensure it works correctly

Triggers are pieces of code that execute before or after specific events occur on a record.

• Triggers can be used to automate processes, enforce business rules, and maintain data consistency.

• Triggers can be written in Apex and are associated with a specific object.

• Triggers can be executed before or after insert, update, delete, or undelete operations.

• Triggers can access and modify related records and perform complex validation logic.

Reverse a given string

• Create a char array from the input string

• Use two pointers to swap characters from start and end of the array

• Repeat until the pointers meet in the middle

Maps in Java are data structures that store key-value pairs and allow for efficient retrieval and manipulation of data.

• Maps in Java are implemented by classes like HashMap, TreeMap, and LinkedHashMap.

• They allow you to store unique keys and their corresponding values.

• You can retrieve values from a map using the key, and also update or remove key-value pairs.

• Example: HashMap<String, Integer> map = new HashMap<>(); map.put("apple", 5); int value = map.get("apple");