PayPal Software Engineer Interview Questions, Process, and Tips

Round duration - 90 minutes
Round difficulty - Medium

late Morning

Q1. 
Painting Fences Problem Statement
You are given ‘N’ fences. Your task is to compute the total number of ways to paint these fences using only 2 colors, such that no more than 2 adjacent fences have the sa...read more
Ans. 
First I had couple of greedy solutions in mind, later on analysis I tried applying dynamic programming approach.
It was working.
Answered Anonymously
Add your answer
Q2. 
Cycle Detection in a Directed Graph
Determine if a given directed graph contains a cycle. Return true if at least one cycle is found, otherwise return false.
Input:
T
The first line consists of the integ...read more
Ans. Using DFS
To change a directed tree to a cyclic directed graph by adding one edge, we can choose a node that has more than zero ancestors and add an edge from that node to one of its ancestors. This can always form a complete cycle. This edge is called the back edge.
 
The basic idea is to traverse a graph using DFS and keep track of visited nodes and search for the back edge. If we found any back edge, we will retur...read more
Answered Anonymously
Add your answer

Round duration - 30 minutes
Round difficulty - Easy

Technical Interview. The round went on for about 20 min

Q1. 
Painter's Partition Problem
You are given an array/list of length 'N'. Each element of the array/list represents the length of a board. There are 'K' painters available to paint these boards. Each unit of...read more
Ans. Dynamic Programming
All we need to do is to Divide the boards into k of fewer partitions such that the maximum sum of the elements in a partition, overall partitions is minimized.
 
We can put the (k - 1)th divider between the ith and (i + 1)th element where i is between 1 and N.
 
Now the recursive function will just require two conditions that can lead to the result and that will be out the maximum total cost:
• Th...read more
Answered Anonymously
Add your answer

Round duration - 30 Minutes
Round difficulty - Easy

Technical interview 2

Q1. 
Cycle Detection in a Singly Linked List
Determine if a given singly linked list of integers forms a cycle or not.
A cycle in a linked list occurs when a node's next points back to a previous node in the ...read more
Ans. 
solved using slow pointer and fast pointer approach.
Answered Anonymously
Add your answer
Q2. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. Brute Force
The brute force approach is to use recursion. First, we reach the end of the Linked List recursively and at last node, we return the last node, which becomes the new head of the partially reversed Linked List. While coming back from each recursion call we add the current node in the current recursion call to the last node of the partially reversed Linked List and assign the current node to null.
 
Steps:
&...read more
Answered Anonymously
Add your answer

Round duration - 40 Minutes
Round difficulty - Medium

Hiring Manger, timing was late morning

Round duration - 60 minutes
Round difficulty - Medium

Technical interview round where the Interviewer asked me questions based on data structures and algorithms.

Q1. 
Design a Constant Time Data Structure
Create a data structure that maintains mappings between keys and values, supporting the following operations in constant time:
1. INSERT(key, value): Add or update t...read more
Add your answer
Q2. 
Integer to Roman Conversion
Given an integer N, convert it to its corresponding Roman numeral representation. Roman numerals comprise seven symbols: I, V, X, L, C, D, and M.
Example:
Input:
N = 2
Outp...read more
Add your answer

Round duration - 60 minutes
Round difficulty - Medium

Technical interview round where the Interviewer asked me questions based on data structures and algorithms.

Q1. 
Total Area of Overlapping Rectangles Problem Statement
Determine the total area covered by two given rectangles on a 2-D coordinate plane, which may have an overlapping area.
Input:
The first line conta...read more
Add your answer
Q2. 
Longest Repeating Subsequence Problem Statement
Given a string st, your task is to determine the length of the longest repeating subsequence such that no two subsequences have the same character at the sa...read more
Add your answer

Round duration - 60 minutes
Round difficulty - Medium

This was a system design round.

Q1. How would you design a rate limiter?
Add your answer

Round duration - 60 Minutes
Round difficulty - Easy

The interview was held in the evening on a weekday, Interview was nice and quite experienced, he asked me about my previous experience in the area and they told me about the team and work for which they were hiring, we did some discussion on that. Meanwhile, I was also asked a few questions on Database and SQL.

Q1. 
Find Magic Index in Sorted Array
Given a sorted array A consisting of N integers, your task is to find the magic index in the given array, where the magic index is defined as an index i such that A[i] = i...read more
Ans. Brute Force Approach
• In this brute force approach, we will check each element one by one and try to find if there is any magic index in the given array or not.
• In this approach, we will initialize our answer variable (say, ans) with ans = -1.
• Then we will iterate in the array one by one (say, loop variable i) from the beginning and check if there is any magic index in our array or not.
• If we find any index in the array suc...read more
Answered Anonymously
Add your answer

Round duration - 60 minutes
Round difficulty - Medium

The interview was in the afternoon. There were some glitches with the teams meeting but it got sorted out in a few minutes. This round was purely coding based. He started with questions on arrays, linked lists, and string manipulation with an increasing level of hardness. The tricky part was that the online editor I was given for writing the code was not an IDE but a simple text editor, so I wasn't getting any help in terms of code completion or syntax errors or syntax highlighting.

Q1. 
Find All Pairs Adding Up to Target
Given an array of integers ARR of length N and an integer Target, your task is to return all pairs of elements such that they add up to the Target.
Input:
The first line ...read more
Ans. Hashing Solution
• We can store the frequency of every element in the array in a hashmap.
• We will loop over every index i, and check the frequency of (Target - ARR[i]) is the hashmap:
  • If (Target - ARR[i]) is equal to ARR[i], we will check if frequency of ARR[i] . If it is greater than 1 then we will decrease the frequency of ARR[i] by 2 and add a pair (ARR[i] , ARR[i]) to our answer.
  • Else, if the frequency of ARR[i] and Targ...read more
Answered Anonymously
Add your answer

Round duration - 60 minutes
Round difficulty - Easy

Technical Interview round where the interviewer asked questions based on Data structures and algorithms.

Q1. 
Reverse Linked List Problem Statement
Given a Singly Linked List of integers, your task is to reverse the Linked List by altering the links between the nodes.
Input:
The first line of input is an intege...read more
Add your answer
Q2. 
Dijkstra's Shortest Path Problem
Given an undirected graph with ‘V’ vertices (labeled 0, 1, ... , V-1) and ‘E’ edges, where each edge has a weight representing the distance between two connected nodes (X,...read more
Add your answer

Round duration - 60 minutes
Round difficulty - Easy

Technical Interview round where the interviewer asked questions based on Data structures and algorithms.

Q1. 
Sort Linked List Based on Actual Values
Given a Singly Linked List of integers that are sorted based on their absolute values, the task is to sort the linked list based on the actual values.
The absolute...read more
Add your answer
Q2. 
Kth Largest Element Problem
Given an array containing N distinct positive integers and a number K, determine the Kth largest element in the array.
Example:
Input:
N = 6, K = 3, array = [2, 1, 5, 6, 3, ...read more
Add your answer

Round duration - 30 minutes
Round difficulty - Easy

HR Round that lasted for around 30 minutes. The interviewer asked questions to know more about me.