Paytm Software Development Engineer Intern Interview Questions and Answers

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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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 - 90 minutes
Round difficulty - Medium

This was an online test for 90 minutes. 2 programming questions and MCQs related to CS fundamentals were asked.

Q1. 
Cycle Detection in a Singly Linked List
Determine if a given singly linked list of integers forms a cycle or not.
A cycle in a linked list occurs when a node's next points back to a previous node in the ...read more
Ans. 
Detect if a singly linked list forms a cycle by checking if a node's next points back to a previous node.
• Traverse the linked list using two pointers, one moving one step at a time and the other moving two steps at a time.

• If the two pointers meet at any point, it indicates the presence of a cycle in the linked list.

• If one of the pointers reaches the end of the list (null), it means there is no cycle.
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Q2. 
Palindrome Partitioning II Problem Statement
Given a string ‘str’, find the minimum number of partitions needed such that every segment of the string is a palindrome.
The task is to make cuts in the stri...read more
Ans. 
Find the minimum number of partitions needed in a string such that every segment is a palindrome.
• Iterate through the string and check for palindromes at each possible partition point.

• Use dynamic programming to keep track of the minimum cuts needed.

• Consider edge cases where the string is already a palindrome or consists of different characters only.
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Round duration - 60 minutes
Round difficulty - Medium

Technical round that lasted for around 60 minutes. The interviewer asked questions related to data structures and algorithms.

Q1. 
DFS Traversal Problem Statement
Given an undirected and disconnected graph G(V, E), where V is the number of vertices and E is the number of edges, the connections between vertices are provided in the 'GR...read more
Ans. 
DFS traversal problem on an undirected and disconnected graph to find connected components.
• Perform Depth First Search (DFS) on each vertex to find connected components

• Use a visited array to keep track of visited vertices

• Print the number of connected components and list vertices in ascending order for each component
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Q2. 
Cycle Detection in Undirected Graph Problem Statement
You are provided with an undirected graph containing 'N' vertices and 'M' edges. The vertices are numbered from 1 to 'N'. Your objective is to determi...read more
Ans. 
Detect cycles in an undirected graph with given vertices and edges.
• Use Depth First Search (DFS) to traverse the graph and detect cycles.

• Maintain a visited array to keep track of visited vertices and a parent array to keep track of the parent of each vertex.

• If while traversing, you encounter a visited vertex that is not the parent of the current vertex, then a cycle exists.

• Consider edge cases like disconnected graphs an
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Round duration - 60 minutes
Round difficulty - Medium

Technical round that lasted for around 60 minutes. The interviewer asked questions related to data structures and algorithms.

Q1. 
Merge Sort Problem Statement
You are given a sequence of numbers, ARR. Your task is to return a sorted sequence of ARR in non-descending order using the Merge Sort algorithm.
Explanation:
The Merge Sort...read more
Ans. 
Implement Merge Sort algorithm to sort a sequence of numbers in non-descending order.
• Implement the Merge Sort algorithm using a Divide and Conquer approach

• Recursively divide the input array into two halves until the size of each array is 1

• Merge the sorted halves to produce a completely sorted array

• Ensure the output is in non-descending order
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Q2. 
Maximum Difference Problem Statement
Given an array ARR of N elements, your task is to find the maximum difference between any two elements in ARR.
If the maximum difference is even, print EVEN; if it is...read more
Ans. 
Find the maximum difference between any two elements in an array and determine if it is even or odd.
• Iterate through the array to find the maximum and minimum elements

• Calculate the difference between the maximum and minimum elements

• Check if the difference is even or odd and return the result
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Q3. What is hashing and how can it be implemented?
Ans. 
Hashing is a process of converting input data into a fixed-size string of bytes using a hash function.
• Hashing is used to securely store passwords by converting them into a hash value before storing in a database.

• Hashing is used in data structures like hash tables to quickly retrieve data based on a key.

• Common hash functions include MD5, SHA-1, and SHA-256.

• Hashing can be implemented in programming languages like Python
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Round duration - 60 minutes
Round difficulty - Easy

Technical Interview round where the interviewer asked questions based on Data structures and algorithms.

Q1. 
Reverse Linked List Problem Statement
Given a Singly Linked List of integers, your task is to reverse the Linked List by altering the links between the nodes.
Input:
The first line of input is an intege...read more
Ans. 
Reverse a singly linked list by altering the links between nodes.
• Iterate through the linked list and reverse the links between nodes.

• Use three pointers to keep track of the current, previous, and next nodes.

• Update the links between nodes to reverse the list.

• Return the head of the reversed linked list.
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Q2. 
Dijkstra's Shortest Path Problem
Given an undirected graph with ‘V’ vertices (labeled 0, 1, ... , V-1) and ‘E’ edges, where each edge has a weight representing the distance between two connected nodes (X,...read more
Ans. 
Dijkstra's algorithm is used to find the shortest path from a source node to all other nodes in a graph with weighted edges.
• Implement Dijkstra's algorithm to find the shortest path distances from the source node to all other nodes.

• Use a priority queue to efficiently select the next node with the shortest distance.

• Update the distances of neighboring nodes based on the current node's distance and edge weights.

• Handle disc...read more
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Round duration - 60 minutes
Round difficulty - Easy

Technical Interview round where the interviewer asked questions based on Data structures and algorithms.

Q1. 
Sort Linked List Based on Actual Values
Given a Singly Linked List of integers that are sorted based on their absolute values, the task is to sort the linked list based on the actual values.
The absolute...read more
Ans. 
Sort a Singly Linked List based on actual values instead of absolute values.
• Traverse the linked list and store the values in an array.

• Sort the array based on actual values.

• Update the linked list with the sorted values.
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Q2. 
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 to easily find the Kth largest element.

• Ensure all elements in the array are distinct for accurate results.

• Handle multiple test cases efficiently by iterating through each case.
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Round duration - 30 minutes
Round difficulty - Easy

HR Round that lasted for around 30 minutes. The interviewer asked questions to know more about me.