Paytm Interview Experience

Paytm Interview Experience

Coding Round 1
Q1 You have to make a necklace with pearls. Minimum number of pearls that can be used is 1 and maximum is n. Each pearl has a magnificence coefficient and the necklace should be such that the pearls are in ascending order of their magnificence. Find such number of necklaces that can be formed with given condition.
Input given is n (no of pearls), Lowest magnificence and highest magnificence.
Example n= 1, LM= 8 HM=9, so there can be 2 cases, one necklace with pearl 8 and one with pearl 9.

Q2 Write a program to find sum of first largest k elements from a given array of integers?


Interview Round 1
Q1 Write a program to print the left view and right view of a tree in single traversal and o(n) time complexity

Q2 Difference between Composition and Inheritance with example? Which is better?

Q3 What is Immutable? Example

Q4 What is strategy pattern? Its real life example

Q5 What is Singleton. Implement one. How will your singleton handle multi-threading and Serialization issues.

Q6 Design Patterns you have used in your project? Write builder pattern and why we use builder pattern with example

Q7 Collections.sort internally uses which sorting algorithm. - It uses stable, adaptive merge sort.
Note: Arrays.sort for primitives uses dual pivot Quick Sort.

Q8 In Spring what is IOC (Inversion of Control) and DI (Dependency Injection).

Q9 Difference between EJB and Spring framework. What Spring offers better than EJB

Q10 Difference between JPA and Hibernate? How are they related or differ.

Q11 What is tomcat - web server or app server? Difference between web server, container and app server?

Q12 What is @Transactional in hibernate?

Q13 What is proxy? Have you used it?

Q14 Design Question - Design autocomplete in google search?
Features, Data Structure, latency and Scalability related questions.

Q15 What is docker? How docker stores its images?

Q16 How database storage works? What is Indexing? How indexing happens in databases and how it improves the search in a database. Brief discussion on BTrees and B+Trees.


Interview Round 2
Q1 Identify various components of a bank? Design schema for bill payment component? Brief discussion on normalization and how to make search faster in the database.

Q2 Write a Spring controller to get customer details by id

Q3 Implement concurrent hashmap. Follow up questions on the same like why no read lock on get method, how many threads will be able to access at once, synchronization issues etc.


Interview Round 3
Q1 Identify various micro-services of uber like application.