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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Q1. Discuss about OWASP features
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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
Ans. 
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
Ans. 
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

There were 3 problems 1 was easy and 2 were of medium types.

Q1. 
Odd Even Levels in Binary Tree
Given a binary tree, the task is to compute the modulus of the difference between the sum of nodes at odd levels and the sum of nodes at even levels.
Input:
The first line...read more
Ans. DFS
1. Create two variables, one for storing the sum of nodes at the odd level and one for storing the sum of nodes at even level.
2. Use the below algorithm to calculate level sums where:
oddSum: denotes sum of nodes at odd levels, initially 0.
evenSum: denotes sum of nodes at ecen levels, initially 0.
level: the level of the current node, initially 1. 
void oddEvenLevelHelper(current, oddSum, evenSum, level)
 
• If the cur...read more
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Q2. 
Rotting Oranges Problem Statement
You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:
• 0 - representing an empty cell
• 1 - representing a fre...read more
Ans. Naïve Solution
The idea is very simple and naive. We will process the rotten oranges second by second. Each second, we rot all the fresh oranges that are adjacent to the already rotten oranges. The time by which there are no rotten oranges left to process will be our minimum time.
 
In the first traversal of the grid, we will process all the cells with value 2 (rotten oranges). We will also mark their adjacent cells ...read more
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Round duration - 50 minutes
Round difficulty - Medium

the interviewer was very polite and straightforward, he didn't ask me to introduce myself and he directly jumps to the coding problems.
What is new about the relationship between the and tags in HTML5?
Explain Components, Modules and Services in Angular

Q1. 
Circular Move Problem Statement
You have a robot currently positioned at the origin (0, 0) on a two-dimensional grid, facing the north direction. You are given a sequence of moves in the form of a string ...read more
Ans. Optimal Approach
Initialize a variable ‘direction’ with 0 which means that the robot is initially facing towards the north.
direction: 0 -> Robot is facing towards the North
direction: 1 -> Robot is facing towards the West 
direction: 2 -> Robot is facing towards the South 
direction: 3 -> Robot is facing towards the West
 
Initialize two variables ‘x’ and ‘y’ as 0. They will represent the position ...read more
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Round duration - 70 minutes
Round difficulty - Easy

What is a View in sql? What are the TRUNCATE, DELETE and DROP statements?

Q1. 
Rotate Matrix by 90 Degrees Problem Statement
Given a square matrix 'MATRIX' of non-negative integers, rotate the matrix by 90 degrees in an anti-clockwise direction using only constant extra space.
Inpu...read more
Ans. Transpose and Reverse
The idea is to find the transpose of the given matrix and then reverse the columns of the transposed matrix. For example:
For the given 2D matrix:
	[ [ 1,  2,  3 ],
	  [ 4,  5,  6 ],
	  [ 7,  8,  9 ] ]
After taking transpose, it will become:
	[ [ 1,  4,  7 ],
	  [ 2,  5,  8 ],
	  [ 3,  6,  9 ] ]
After reversing the columns, it will ...read more
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Q2. 
Minimum Characters to Make a String Palindrome
Given a string STR of length N, determine the minimum number of characters to be added to the front of the string to make it a palindrome.
Input:
The first...read more
Ans. Brute Force
• The idea is pretty simple, as we can add only at the front, thus, we need to work on the prefix of the string.
• We need to find the largest prefix that is a palindrome. For example, in case of “abbac”, the largest prefix that is a palindrome is “abba”, now all you need to do is add the reverse of left out suffix i.e. “ca” at the front to make it a palindrome.
• This can be done in the following way:-
  • Until the str...read more
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Round duration - 20 minutes
Round difficulty - Easy

Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
Longest Palindromic Subsequence Problem Statement
Given a string A consisting of lowercase English letters, determine the length of the longest palindromic subsequence within A.
Explanation:
• A subsequ...read more
Ans. Recursive Approach
The main idea behind this approach is to use recursion. The idea is to compare the first character of the string A[i..j] with its last character. There are two possibilities:
1. If the first character of the string is the same as the last character, we include first and last characters in the palindrome and do a recursive call for the remaining substring A[i + 1, j - 1].
2. If the last character of the string...read more
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Q2. 
Word Pattern Problem Statement
Given two strings S and T, determine if S follows the same pattern as T.
A full match means there is a bijection between a letter of T and a non-empty word of S.
Example:
...read more
Ans. Hashmap
We will use two hashmaps ‘charToWord’ and ‘wordToChar’ to track which character of ‘T’ maps to which word of ‘S’ and which word of ‘S’ maps to which character of ‘T’,  respectively.
 
Here is the algorithm:
1. We initialise two hashmaps ‘charToWord’ and ‘wordToChar’.
2. We scan each character-word pair
   1. If the character is not present in ‘charToWord’ 
      1. If the word is already present in ‘wordToChar’ 
         1. Return ...read more
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Round duration - 40 Minutes
Round difficulty - Easy

Q1. 
Level Order Traversal Problem Statement
Given a binary tree of integers, return the level order traversal of the binary tree.
Input:
The first line contains an integer 'T', representing the number of te...read more
Ans. Breadth First Search
In the level order traversal, we will be using queue data structure which has the property FIRST IN FIRST OUT that’s why which nodes come first in current level the children of that node will also come first for the next level. So, we visit all the nodes one by one of the current level and push into the queue so that when we will be complete with the current level, then we can start exploring nodes ...read more
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Q2. 
Next Greater Node in Linked List Problem Statement
In a set of linked ninja villages, the goal is to determine if a stronger ninja exists in the nearest village linked ahead. Given a linked list of 'N' in...read more
Ans. Brute Force
We will iterate through the given linked list of elements (nodes) with the help of two nested loops. Where we will check for every node whether there exists a next node with a value bigger than the value of current node and subsequently build the ‘ans’ list (array) and return it.
 
The algorithm will be-
 
1. We will run a loop for the starting node (head) of the given linked list.
2. From every node we will ...read more
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Round duration - 15 Minutes
Round difficulty - Easy