Role: Software Engineer
College: Not Specified (On-Campus)
Interview Date: Not Specified (Article updated July 23, 2025)
Interview Type: On-Campus
Result: Selected
Difficulty: Medium to Hard
Rounds: Online Test + 4 Technical Rounds + 1 HR Round
Topics Asked: Data Structures, Algorithms, DBMS, OS, Design Patterns, Networking, System Design, Problem Solving
Experience:
PayU visited the campus for recruitment. The selection process included an Online Test, four Technical Rounds, and one HR Round.
Online Test: Consisted of 15 technical MCQs and 5 coding questions. The candidate solved all coding questions and about 10 technical questions, leading to a shortlist for personal interviews.
Technical Interview 1 (30 mins):
- Introduce yourself.
- Tell me about your projects.
- Code for a modified Least Common Ancestor (LCA) of two nodes in a BST (complete working code with boundary conditions).
- How is security provided on a network?
- DBMS: Discussion on Normalization and its significance, various Normal Forms (1NF, 2NF, 3NF, BCNF).
- OS: Explain Paging with an example.
- Design Patterns: Implement Singleton Design Pattern (with a hint).
- Some easy questions on Arrays.
- Write code for Vertical Tree Traversal (considering all boundary and test cases).
- "English Dictionary" question (which the candidate had already solved).
- Asked if the candidate had any questions.
Technical Interview 2 (45 mins):
- Introduce yourself.
- Write complete code for insertion and deletion in AVL Trees implemented using maps (candidate mentioned this as a project, but couldn't write complete code, so explained it instead).
- Discussion about how to maintain user sessions on the web.
- Discussion about cookies and their significance.
- Given an array of integers, find all pairs with a given sum K.
- Given an array of integers, find all pairs (a, b) such that (a % b) = k (O(N) solution expected).
Technical Interview 3 (50 mins):
- Given some input and corresponding output, write code to get the required outputs. This round checked understanding of Recursion, base cases, and problem-solving approach. Code was needed for every case, with increasing complexity of inputs.
- How to implement Mutual Friend Feature of Facebook.
- How to implement top 5 friends feature.
Technical Interview 4 (40 mins):
- Introduce yourself.
- What is KMP Algorithm? Write code for the preprocessing function.
- Difference between HTTP and HTTPS.
- Given two strings, remove characters from string1 that appear in string2 in O(N) and constant space (code was needed).
- Modified DP problem of Rod Cutting (no code needed, mathematical equations and DP approach explanation).
HR Round (20 mins):
- Introduce yourself.
- Why PayU?
- Most challenging situation during college projects and how it was solved.
- Strengths.
- Weaknesses.