Juspay Technologies Software Development Engineer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Easy

Technical Interview Round with questions based on Data structures, OOPS and SQL.

Q1. 
Delete a Node from a Linked List
You are provided with a linked list of integers. Your task is to implement a function that deletes a node located at a specified position 'POS'.
Input:
The first line co...read more
Ans. 
Implement a function to delete a node from a linked list at a specified position.
• Traverse the linked list to find the node at the specified position.

• Update the pointers of the previous and next nodes to skip the node to be deleted.

• Handle edge cases such as deleting the head or tail of the linked list.

• Ensure to free the memory of the deleted node to avoid memory leaks.
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Q2. Write an SQL query to find the nth highest salary.
Ans. 
SQL query to find the nth highest salary
• Use the ORDER BY clause to sort salaries in descending order

• Use the LIMIT and OFFSET clauses to skip the first n-1 highest salaries

• Combine the above steps in a single query to find the nth highest salary
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Q3. Can you explain the concepts of Object-Oriented Programming (OOP)?
Ans. 
OOP is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.
• OOP focuses on creating objects that interact with each other to solve problems.

• Key concepts include encapsulation, inheritance, and polymorphism.

• Encapsulation involves bundling data and methods that operate on the data into a single unit.

• Inheritance allows classes to inherit at...read more
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Round duration - 60 minutes
Round difficulty - Easy

Was asked me about my favorite technologies, What i liked about Facebook. And asked me to design a cinema ticket reservation web site­ like the one satyam has.

Q1. 
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
Ans. 
Find the Kth largest element in an array of distinct positive integers.
• Sort the array in non-increasing order and return the Kth element.

• Handle multiple test cases efficiently.

• Ensure all elements in the array are distinct.
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Q2. What are virtual functions?
Ans. 
Virtual functions are functions in a base class that are overridden in derived classes to achieve runtime polymorphism.
• Virtual functions are declared in a base class with the 'virtual' keyword.

• They are overridden in derived classes using the 'override' keyword.

• They allow a function to be called based on the runtime type of an object.

• Virtual functions enable dynamic binding and late binding in C++.

• Example: virtual void ...read more
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Q3. Design a Cinema Ticket Reservation System.
Ans. 
Design a Cinema Ticket Reservation System
• Use a database to store movie information, showtimes, and seat availability

• Allow users to search for movies, select showtimes, and choose seats

• Implement a payment system for ticket purchases

• Send confirmation emails with QR codes for ticket validation
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Q4. In how many attempts can you find a defective ball among 10 given balls using a two-pan balance scale?
Ans. 
You can find a defective ball among 10 given balls in 2 attempts using a two-pan balance scale.
• Divide the 10 balls into two groups of 5 each.

• Weigh the two groups on the balance scale.

• If one group is heavier, it contains the defective ball. If they are equal, the defective ball is in the remaining 5 balls.

• Divide the group of 5 balls with the defective one into two groups of 2 and 3 balls.

• Weigh the two groups on the bala...read more
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Round duration - 30 minutes
Round difficulty - Easy

HR round that lasted for about 30 minutes. The interviewer asked me questions to know more about me and a puzzle.

Q1. Can you tell me about your projects and your extracurricular activities?
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Round duration - 60 minutes
Round difficulty - Easy

I couldn't find an optimal approach to the first question, so she skipped that question and proceeded to next questions. Remaining questions I have answered satisfactorily.

Q1. 
Subset Sum Equal To K Problem Statement
Given an array/list of positive integers and an integer K, determine if there exists a subset whose sum equals K.
Provide true if such a subset exists, otherwise r...read more
Ans. 
Given an array of positive integers and an integer K, determine if there exists a subset whose sum equals K.
• Use dynamic programming to solve this problem efficiently

• Create a 2D array to store if a subset with a particular sum exists

• Iterate through the array and update the 2D array accordingly

• Check if the value at the end of the iteration is true for the given K
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Q2. 
BFS Traversal in a Graph
Given an undirected and disconnected graph G(V, E) where V vertices are numbered from 0 to V-1, and E represents edges, your task is to output the BFS traversal starting from the ...read more
Ans. 
BFS traversal in a disconnected graph starting from vertex 0.
• Implement BFS algorithm to traverse the graph starting from vertex 0.

• Use a queue to keep track of visited nodes and their neighbors.

• Ensure to print the traversal sequence in the correct order.

• Handle disconnected components by checking for unvisited nodes.

• Follow the BFS approach of exploring neighbors before moving to the next level.
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Round duration - 60 minutes
Round difficulty - Easy

I told that my strength is problem solving and I can always find a way when there is a bottle-neck. Gave some examples of my experiences while doing my assignments.

Q1. 
Replace Spaces in a String
Given a string STR consisting of words separated by spaces, your task is to replace all spaces between words with the characters "@40".
Input:
The first line contains an integ...read more
Ans. 
Replace spaces in a string with '@40'.
• Iterate through each character in the string

• Replace spaces with '@40'

• Return the modified string
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You should be familiar with core java features. Collections, converting one collection Array / Vector to other. Removing duplicates. Lambda chaining / Functional programming. Basic SQL - Joins, Aggregates etc.

Q1. Explain Architecture of applications you worked on. Justify use of components. System Design questions.
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Q1. Internal Implementation of HashMap
Ans. 
HashMap is implemented using an array of linked lists to handle collisions.
• HashMap stores key-value pairs in an array of linked lists

• Hash function is used to determine the index of the array where the key-value pair will be stored

• Collision handling is done by chaining, where multiple key-value pairs with the same hash value are stored in the same linked list

• HashMap allows null keys and values

• HashMap is not synchronized...read more
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1hr aptitude + coding