PayPal Full Stack Engineer Interview Questions and Answers

Q1. Sal queries simeple data structure question finding largest number in am array.
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Q2. Solid principal
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It will be a basic maths questions.

As a general topic of trend in world.

To be known for programming knowledge about us.

Q1. Programming oridanited
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Q2. Skill knowledge questions
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Q1. Tell me about your self.
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Q2. Family background .
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Q1. What are the java 1.8 features?
Ans. 
Java 1.8 introduced several new features including lambda expressions, functional interfaces, streams, and default methods.
• Lambda expressions allow you to write code in a more concise and readable way.

• Functional interfaces are interfaces with a single abstract method, used for lambda expressions.

• Streams provide a way to work with sequences of elements and perform operations on them.

• Default methods allow interfaces to h...read more
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Q2. Write program to print element sorting by using java 8 feature.
Ans. 
Program to print elements sorted using Java 8 features
• Use Stream API to sort the elements

• Use lambda expressions for sorting

• Use the sorted() method to sort the elements
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Q1. Experience in ReactJS
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I have 2 years of experience in ReactJS, including building interactive user interfaces and integrating with backend services.
• Developed a responsive web application using ReactJS, Redux, and Material-UI

• Implemented RESTful APIs to fetch and update data in the application

• Utilized React Router for client-side routing and navigation

• Worked on optimizing performance by using memoization and lazy loading techniques
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Q2. Experience in Spring Boot
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Q1. What is react and why are we using it
Ans. 
React is a JavaScript library for building user interfaces.
• React allows for building reusable UI components

• It uses a virtual DOM for efficient updates

• React is declarative, making it easier to reason about code

• It is widely used in web development for its performance and flexibility
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Q2. What is redux in react
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Redux is a predictable state container for JavaScript apps.
• Redux is a state management library for React

• It helps in managing the state of the application in a predictable manner

• It follows a unidirectional data flow pattern

• It has three main components: store, actions, and reducers

• Store holds the state of the application

• Actions are plain JavaScript objects that describe what happened

• Reducers specify how the application's...read more
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Create a react app with redux

Round duration - 70 minutes
Round difficulty - Medium

The test started around 3 pm and was of 70 minutes. 3 coding questions were asked which were mainly on trees and number theory.

Q1. 
Factorial Calculation Problem Statement
Develop a program to compute the factorial of a given integer 'n'.
The factorial of a non-negative integer 'n', denoted as n!, is the product of all positive integ...read more
Ans. Using while() loop
• This can be done using an if-else-if ladder to check for negative,0, and positive numbers.
• If the input is a positive number use a while loop to multiply n with n-1, n-2…1 and get the desired output.
Space Complexity: O(1)Explanation: Time Complexity: O(1)Explanation:
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Q2. 
Next Greater Element Problem Statement
Given a list of integers of size N, your task is to determine the Next Greater Element (NGE) for every element. The Next Greater Element for an element X is the firs...read more
Ans. Brute Force
For every element in the array, we will run a loop on its right side. As soon as we find an element on its right side which is greater than it, we will break the loop, assign it as the NGE of this element, move forward, and do the same for the next element.
Space Complexity: O(1)Explanation:
O(1)
 
No extra space is used.
Time Complexity: O(n^2)Explanation:
O(N ^ 2),  Where N is the number of elements ...read more
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Q3. 
Ceil Value from BST Problem Statement
Given a Binary Search Tree (BST) and an integer, write a function to return the ceil value of a particular key in the BST.
The ceil of an integer is defined as the s...read more
Ans. Brute Force
We will traverse the Binary search tree from the root node till we find the node whose key value is given, and upon getting that, we return the ceil value of it.

 
The steps are as follows:  
• Initialize ‘ceilValue’ to store the ceil value to be returned.
• We run a while loop till the value of the node is not equal to NULL.
  • If the value of the node is equal to ‘X’’ then we return the node value.
  • If th...read more
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Round duration - 60 minutes
Round difficulty - Medium

Interviewer was very friendly and supportive. My interview happened on google meet. What is a View? What is Denormalization? Difference between “==” and “===” operators in js.

Q1. 
Sub Sort Problem Statement
You are given an integer array ARR. Determine the length of the shortest contiguous subarray which, when sorted in ascending order, results in the entire array being sorted in a...read more
Ans. Brute Force
In this approach, we consider every possible subarray that can be formed from the given array ‘ARR’. For every subarray ARR[i … j] considered, we need to check whether this is the smallest unsorted subarray or not.
 
The algorithm is as follows:
1. Let’s take the variable ‘ANS’ equal to 'N' (the length of the array) initially.
2. Now for every subarray ARR[i … j], we will find the maximum and minimum value lying ...read more
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Q2. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. Sorting
Use any good sorting algorithm like Merge Sort, Quick Sort or inbuilt sorting function of different languages.
• Sort the Array and just return.
Space Complexity: O(1)Explanation:
O(1), As we are using constant space.
Time Complexity: O(nlogn)Explanation:
O(N*log(N)), where ‘N’ is the size of the array.
We are using inbuilt sort algorithm which has Overall Time Complexity O(N*log(N))
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Round duration - 60 minutes
Round difficulty - Medium

What are some of the advantages of Angular over other frameworks?

Q1. 
Cousin Nodes in a Binary Tree
Determine if two nodes in a binary tree are cousins. Nodes are considered cousins if they are at the same level and have different parents.
Explanation:
In a binary tree, e...read more
Ans. Recursive Solution
• Find the levels of both the given nodes.
• This can be done by making a separate function for finding the level/by using level order traversal.
• The levels should be the same.
• Check if both the nodes are siblings or not.
• This can again be done by simply going through the entire Binary Tree and checking if the node’s children are the given two nodes. If this is true, then given two nodes are siblings and henc...read more
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Round duration - 10 minutes
Round difficulty - Easy

I got a call from HR in the evening around 6:30 pm.

Q1. Can you tell me about yourself?
Ans. 
Tip 1 : Do prepare such questions before hand only.
Tip 2 : Speak confidently.
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Q2. How was your experience with the previous two technical rounds?
Ans. 
Tip 1 : Do remember the names of the interviewers who took your interview.
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Q3. What do you know about Paytm?
Ans. 
Tip 1 : Do a research before hand about what does the company do.
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Easy questions were asked. Practice aptitude questions from net along with javascript

Q1. Write a servlet in java
Ans. 
A servlet in Java is a server-side component that extends the capabilities of servers.
• Create a class that extends HttpServlet

• Override the doGet or doPost method

• Implement the logic for handling requests and generating responses

• Register the servlet in web.xml or using annotations
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Q2. Sql queries and jdbc questions
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