Persistent Systems Data Engineer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Medium

Timing was in the morning around 10 am. This round was conducted on Hackerrank and contained 2 coding questions of easy to medium level which varied for all the students taking the test. There were 20 MCQs from topics like Java, Operating Systems, Data structures, and SQL.
I also gave a test for this company last year during internships. At that time MCQs were based on aptitude and reasoning. Also at that time, there were 2 coding questions and timing was dividing according to sections.

Q1. 
Nth Element Of Modified Fibonacci Series
Given two integers X and Y as the first two numbers of a series, and an integer N, determine the Nth element of the series following the Fibonacci rule: f(x) = f(x...read more
Ans. 
Calculate the Nth element of a modified Fibonacci series given the first two numbers and N, with the result modulo 10^9 + 7.
• Implement a function to calculate the Nth element of the series using the Fibonacci rule f(x) = f(x - 1) + f(x - 2)

• Return the answer modulo 10^9 + 7 due to the possibility of a very large result

• The series starts with the first two numbers X and Y, and the position N in the series
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Q2. 
Consonant Counting Problem Statement
Given a string STR comprising uppercase and lowercase characters and spaces, your task is to count the number of consonants in the string.
A consonant is defined as a...read more
Ans. 
Count the number of consonants in a given string containing uppercase and lowercase characters and spaces.
• Iterate through each character in the string and check if it is a consonant (not a vowel).

• Keep a count of the consonants encountered while iterating through the string.

• Return the total count of consonants at the end.
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Round duration - 45 Minutes
Round difficulty - Medium

This round was conducted on Cisco WebEx and the interviewer was very friendly. Firstly, we were asked briefly to introduce ourselves. Then he moved on to the CV and asked various questions about the projects, certifications, and internships mentioned. He asked about the implementation of a few features in some of the projects and also about the challenges I faced while doing the project and how I finally overcome the challenge. He also asked about various skills mentioned in the resume.

Q1. 
Merge Two Sorted Linked Lists Problem Statement
You are provided with two sorted linked lists. Your task is to merge them into a single sorted linked list and return the head of the combined linked list.
...read more
Ans. 
Merge two sorted linked lists into a single sorted linked list with constant space complexity and linear time complexity.
• Create a dummy node to start the merged list

• Compare the values of the two linked lists and append the smaller value to the merged list

• Move the pointer of the merged list and the pointer of the smaller value's linked list

• Continue this process until one of the linked lists is fully traversed

• Append the ...read more
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Round duration - 30 Minutes
Round difficulty - Easy

This round started with my Introduction. Then he moved on to behavioral questions just to get an understanding of how we deal with situations and our thinking process.