WinZO Principal Engineer Interview Questions and Answers

There will be 3 coding questions. They are of medium and hard level.

Q1. Sort array consisting 0's 1's and 2's without inbuilt functions
Ans. 
Sort an array of 0's, 1's, and 2's without using inbuilt functions.
• Use three pointers to keep track of the last index of 0's, 1's, and 2's

• Iterate through the array and swap elements based on their value

• Continue until all elements are sorted
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Q1. Os cn related questions
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Q1. Java questions and general hr questions
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Q1. Introduction and technical questions.
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Q2. What is the use of JAVA API?
Ans. 
The JAVA API is a collection of pre-written classes and interfaces that provide ready-to-use functionality for Java developers.
• The JAVA API allows developers to save time and effort by using pre-built code for common tasks.

• It provides a wide range of classes and interfaces for various purposes such as file handling, networking, database connectivity, GUI development, etc.

• Developers can leverage the API to access system...read more
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Q3. Questions are picked from Leetcode.
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The duration of the test is one hour and four coding questions are asked.

Aptitude test question logical reasoning and cheking availablity.

It's test last test and skill related to C ,Java, HTML

4 Coding Questions Were Given.
Check Palindrome String
Longest Increasing Subsequence
Group Anagrams
Add Two Numbers(Linked List)

Questions were picked from leetcode but the restriction of not using any inbuild function made them difficult to solve in the given time frame.

Q1. Basic Java Technical Questions
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Q2. Throws Vs Throw
Ans. 
Throws is used for checked exceptions in Java, while throw is used to explicitly throw an exception.
• Throws is used in method signature to declare that the method may throw a checked exception.

• Throw is used to actually throw an exception in the code.

• Example: public void method() throws IOException { //code }

• Example: throw new IOException();
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Q3. Method Overriding Basics and Output-Based Questions
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Q4. Springboot annotations
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Q5. Inheritance and Concept of Abstract Classes and Interfaces
Ans. 
Inheritance allows a class to inherit properties and behaviors from another class. Abstract classes cannot be instantiated and can have abstract methods. Interfaces define a contract for classes to implement.
• Inheritance allows a class to inherit properties and behaviors from another class

• Abstract classes cannot be instantiated and can have abstract methods

• Interfaces define a contract for classes to implement
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Q1. Rate yourself in js, node js, react, MongoDB (separately)
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Q2. Typeof null, typeof undefined, typeof {}, typeof NaN
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Q3. What changes came in es6
Ans. 
ES6 introduced several new features and improvements to JavaScript, making it more powerful and efficient.
• Arrow functions for more concise syntax

• Let and const for block-scoped variables

• Classes for easier object-oriented programming

• Template literals for easier string interpolation

• Default parameters and rest parameters for function arguments

• Destructuring assignment for easier data extraction

• Promises for asynchronous prog
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Q4. This keyword, closures, hoisting
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Q5. Are let and cont variables hoisted?
Ans. 
Yes, let and const variables are hoisted but not initialized.
• let and const variables are hoisted to the top of their block scope, but they are not initialized until the actual line of code is executed.

• This means that you cannot access a let or const variable before it is declared in the code.

• For example, trying to access a let variable before it is declared will result in a ReferenceError.
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Q6. What is global context
Ans. 
Global context refers to the overall environment or setting in which something exists or operates.
• Global context encompasses all variables, functions, and objects that are accessible throughout an entire program.

• It can be thought of as the 'big picture' view of a program's execution.

• In web development, global context includes the window object in JavaScript.
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Q7. What is temporal deadzone
Ans. 
Temporal dead zone is a period during the variable creation process where accessing the variable results in a ReferenceError.
• Occurs when trying to access a variable before it has been declared with let or const

• Happens due to the variable being in the temporal dead zone until it is declared

• Example: accessing a variable before its declaration will result in a ReferenceError
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Q8. What is modules? types of modules in nodejs
Ans. 
Modules in Node.js are reusable blocks of code that encapsulate related functionality.
• Modules in Node.js can be built-in modules like fs (file system) or third-party modules like express.

• Modules help in organizing code into separate files for better maintainability and reusability.

• Modules can be imported using the require() function in Node.js.
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Q9. Index in mongodb, why we need index, is index good or bad?
Ans. 
Indexes in MongoDB improve query performance by allowing the database to quickly locate and retrieve specific documents.
• Indexes help to speed up query performance by allowing the database to quickly locate specific documents based on the indexed fields.

• Without indexes, MongoDB would have to perform a collection scan, which can be slow and resource-intensive.

• Indexes can be created on single fields or compound fields to ...read more
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Q10. What are hooks , use of useRef
Ans. 
Hooks are a feature in React that allow you to use state and other React features in functional components. useRef is a hook that allows you to create a mutable object that persists for the lifetime of the component.
• Hooks are used to add state and lifecycle methods to functional components in React

• useRef is used to create a mutable reference that persists between renders

• useRef can be used to access DOM elements directl
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Q11. Fs module, http module, worker thread?
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Q12. Why we use mongoose not mongodb driver?
Ans. 
Mongoose is an Object Data Modeling (ODM) library for MongoDB that provides a higher level of abstraction and simplifies interactions with the database.
• Mongoose provides schema validation which helps maintain data integrity.

• Mongoose simplifies querying and data manipulation with built-in functions.

• Mongoose supports middleware functions for pre and post processing of data operations.
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There are three sections: -
1. Quants
2. English
3. Reasoning
All sections are accessible medium but you have maintained the speed and accuracy.
after that coding snippet are in java/python.

Code snippets are there in coding sections.

Q1. Search in 2d matrix
Ans. 
Search for a target value in a 2D matrix efficiently.
• Use binary search on rows to find the potential row where the target value may exist.

• Then use binary search on that row to find the target value.
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Q2. Find quadraplets that sum to target
Ans. 
Find quadraplets in an array that sum up to a target value.
• Use a nested loop to iterate through all possible combinations of quadraplets.

• Keep track of the sum of each quadraplet and compare it to the target value.

• Return the quadraplets that match the target sum.
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