Pubmatic Interview Experience for Software Engineer (On-Campus) 2023

Pubmatic visited my campus hiring for a Software Engineer role on 8th August 2022. 

Job Requirements: 

• Excellent Problem solving and analytical skills.
• Knowledge of Operating Systems concepts.
• Ability to code using any programming language, viz. C, Java, Scala.
• Good understanding of data structures and algorithms.  
• Knowledge of SQL and databases.
• Good fundamental understanding of software engineering.
• Ability to communicate thoughts appropriately.

HackerRank Test:

• 15 questions, 90 minutes
• 2 coding questions, 15 MCQs

Coding 1 – Shortest Substring: Given a string consisting of repeating small case letters, find the shortest substring such that removing it will result in a string that has only unique characters. 

Example: s = xabcadefaga

Coding 2 – Max Score: Given a sequence of integers, find a shuffle of that sequence such that there are as many elements in the new sequence that are larger than elements in the original sequence at their respective indices.

Example: 1 1 2 2 3 6
new seq: 2 2 3 6 1 1 

MCQ questions were CS fundamentals like OS, networking, and C++. 

33 students were selected out of 500+. 

Technical Interview 1: The interview lasted for 1.30 hrs. Total 4 questions. 

1. Scraping: How do you scrape data, and what approaches are used for different websites? 
2. Scraping: To scrape a website containing sub-categories like E-commerce, which is preferred – DFS or BFS. 
3. Coding 1: https://www.geeksforgeeks.org/find-index-first-1-infinite-sorted-array-0s-1s/
4. Coding 2: https://www.geeksforgeeks.org/inorder-successor-in-binary-search-tree/

The interviewer gave liberty of choice for programming language. I used Python. After about 4-5 hours HR sent me a mail for a second interview. 

Technical Interview 2: This interview was with the Manager. He told me that they use C in the team and I would have to use C only in this interview. Before the interview started, he looked at his resume. I had 10+ months of experience in Data Science and Python so he offered to recommend me to a team using Python. I said I will try with C, but if it doesn’t work out then you can recommend me. 

Because Pubmatic works at a very huge scale and performance are very crucial, they focus more on logic than using libraries or even inbuilt functions. So he asked to not use any library like String.h functions and implement them if needed. 

Coding 1: https://www.geeksforgeeks.org/program-to-validate-an-ip-address/

After this, there were some basic Linux questions. 

This interview lasted 1 hour. 

After about an hour, HR scheduled another interview. This time it was second technical interview 2, probably after the recommendation to the Python team. 

2nd Round (Technical Interview 2): This interview was a cakewalk for me because it was in Python. He also asked me some SQL questions. 

1. SQL query: Given two tables Employee and Salary, find the Employee name with the second highest salary. 
2. Coding 1: Implement a linked list. Insert values from 2-5 into it. Print it. Reverse it. 
3. Coding 2: Given a string consisting of words, reverse the sequence of words without using split() method. Also, ignore multiple whitespaces. 

Example: "this is a word" -> "word a is this" 

This interview also lasted for about an hour. 

This process lasted for 2 days. 9 students were selected.