Penny Software Interview Questions and Answers

Q1. Advantage and disadvantage of framework.
Ans. 
Frameworks provide structure and pre-built components for software development, but can also limit flexibility and require learning curve.
• Advantage: Provides structure and pre-built components for faster development

• Advantage: Can improve code quality and maintainability

• Disadvantage: Can limit flexibility and customization

• Disadvantage: Requires learning curve and potential dependency issues

• Example: ReactJS provides a fr...read more
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Q1. What is Oops? Advantage and disadvantage
Ans. 
Oops stands for Object-Oriented Programming. It is a programming paradigm that uses objects to represent real-world entities.
• Advantages: code reusability, modularity, encapsulation, inheritance, polymorphism

• Disadvantages: complexity, steep learning curve, performance overhead

• Example: creating a class 'Car' with properties like 'make', 'model', and 'year', and methods like 'start_engine' and 'stop_engine'
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Round duration - 50 minutes
Round difficulty - Easy

This was a Data Structural round.

Q1. 
Distinct Islands Problem Statement
Given a two-dimensional array/list consisting of integers 0s and 1s, where 1 represents land and 0 represents water, determine the number of distinct islands. A group of...read more
Ans. 
Count the number of distinct islands in a 2D array of 0s and 1s.
• Identify islands by performing depth-first search (DFS) on the grid

• Use a set to store the shape of each island and check for duplicates

• Consider translations to determine distinct islands
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Round duration - 50 minutes
Round difficulty - Easy

This was a Data Structural round.

Q1. 
Word Wrap Problem Statement
You are tasked with arranging 'N' words of varying lengths such that each line contains at most 'M' characters, with each word separated by a space. The challenge is to minimiz...read more
Ans. 
The goal is to minimize the total cost of arranging 'N' words on each line with a maximum character limit 'M'.
• Calculate the cost of each line as the cube of extra space characters needed to reach 'M'.

• Minimize the total cost by arranging words to fit within the character limit on each line.

• Ensure each word appears fully on one line without breaking across lines.
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Round duration - 60 minutes
Round difficulty - Easy

This was a System Design round.

Q1. Can you design a system similar to Red Bus that can handle bookings and onboard both vendors and customers to the platform?
Ans. 
Design a system similar to Red Bus for handling bookings and onboarding vendors and customers.
• Implement a user-friendly interface for customers to search and book tickets

• Create a vendor portal for vendors to manage their offerings and availability

• Include payment gateway integration for secure transactions

• Develop a robust backend system for managing bookings, cancellations, and refunds

• Utilize a database to store user in...read more
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Round duration - 50 minutes
Round difficulty - Easy

This was a System Design round

Round duration - 50 minutes
Round difficulty - Easy

This was an HR round.

Round duration - 1 hour
Round difficulty - Medium

Q1. 
First Missing Positive Problem Statement
You are provided with an integer array ARR of length 'N'. Your objective is to determine the first missing positive integer using linear time and constant space. T...read more
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Round duration - 90 minutes
Round difficulty - Easy

This round was the online coding test conducted on the platform Mettl. The languages allowed were C, C++, Java and Python. There were three questions. One was of graphs (Depth-first search), other was a big integer problem and the third was a string problem.

Q1. 
Graph Coloring Problem Statement
You are provided with a graph consisting of N vertices, numbered from 1 to N, and M edges. Your task is to color the graph using two colors, Blue and Red, such that no two...read more
Ans. 
Given a graph with vertices and edges, determine if it can be colored using two colors without adjacent vertices sharing the same color.
• Check if the graph is bipartite using graph coloring algorithm like BFS or DFS.

• If the graph is bipartite, return 'Possible' with a valid coloring assignment.

• If the graph is not bipartite, return 'Impossible'.
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Q2. 
String Compression Problem Statement
Write a program to perform basic string compression. For each character that repeats consecutively more than once, replace the consecutive duplicate occurrences with t...read more
Ans. 
Write a program to compress a string by replacing consecutive duplicate characters with the character followed by the number of repetitions.
• Iterate through the string and count consecutive occurrences of each character

• Append the character and its count to a new string

• Return the compressed string if it is shorter than the original, else return the original string

• Handle edge cases like single characters or when compresse...read more
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Round duration - 60 minutes
Round difficulty - Easy

This was a pen and paper subjective interview round. You were expected to write full code on paper. Make sure you use proper names for the variables and write comments explaining very clearly what the code does. Also, try writing code in good handwriting which can be understood by the interviewer.

Q1. Find the total number of palindromic substrings in a given string.
Ans. 
Count total palindromic substrings in a given string.
• Iterate through each character in the string and consider it as the center of a palindrome. Expand outwards to find all palindromic substrings.

• Use dynamic programming to efficiently check if a substring is a palindrome.

• Consider both odd-length and even-length palindromes.

• Example: Input 'ababa', output 7 (a, b, a, b, a, aba, aba)
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Round duration - 45 minutes
Round difficulty - Easy

The interview took place in the morning and the interviewer was very friendly.

Q1. 
Count Inversions Problem Statement
Let A[0 ... n-1] be an array of n distinct positive integers. An inversion of A is a pair of indices (i, j) such that i < j and A[i] > A[j]. Given an integer array...read more
Ans. 
Count the number of inversions in an array of distinct positive integers.
• Use merge sort algorithm to count inversions efficiently.

• Divide the array into two halves and recursively count inversions in each half.

• Merge the two sorted halves while counting split inversions.

• Time complexity can be optimized to O(n log n) using merge sort.

• Example: For input A = [2, 4, 1, 3, 5], the output should be 3.
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Q2. 
Sum Tree Conversion Problem Statement
Transform a given binary tree into a sum tree where each node is replaced by the sum of its immediate children's values. Leaf nodes should be replaced with 0. Then, p...read more
Ans. 
Convert a binary tree into a sum tree by replacing each node with the sum of its children's values, and return the preorder traversal.
• Traverse the tree recursively and replace each node with the sum of its children's values

• Leaf nodes should be replaced with 0

• Perform a preorder traversal on the transformed sum tree to get the final result
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Round duration - 30 minutes
Round difficulty - Easy

The HR Interview round was held in the morning and it was right after my technical interview.

It was quite good

Assignment was real world based

Round duration - 60 Minutes
Round difficulty - Easy

It was a hangout video call. The interviewer asked me these questions. Tell me about yourself and 1 coding question.

Q1. 
Special Numbers Problem Statement
Your task is to find the total count of special numbers within a range from 1 to a given integer, 'MAXVAL'. A special number is defined as a number whose digits, when rot...read more
Ans. 
Count the total number of special numbers within a given range by rotating digits 180 degrees.
• Create a function to check if a number is a special number by rotating its digits.

• Iterate through the range from 1 to MAXVAL and count the special numbers.

• Handle the digit rotation mapping for 0, 1, 6, 8, 9.

• Return the count of special numbers for each test case.
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Round duration - 60 Minutes
Round difficulty - Easy

This was an On-site (Behavioural Round) interview. He asked me these questions.

Round duration - 60 Minutes
Round difficulty - Easy

This was another On-site ( DS & Algo) algorithm.

Q1. 
Covid Vaccination Distribution Problem
As the Government ramps up vaccination drives to combat the second wave of Covid-19, you are tasked with helping plan an effective vaccination schedule. Your goal is...read more
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Round duration - 60 Minutes
Round difficulty - Easy

Another On-site ( DS & Algo) interview.

Q1. 
Painter's Partition Problem Statement
Given an array/list representing boards, where each element denotes the length of a board, and a number ‘K’ of available painters, determine the minimum time required...read more
Ans. 
Determine the minimum time required to paint all boards with given constraints.
• Use binary search to find the minimum and maximum possible time to paint all boards.

• Iterate through the boards and assign them to painters based on the time constraints.

• Calculate the total time taken to paint all boards with the assigned painters.
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Q2. 
Chocolate Distribution Problem
You are given an array/list CHOCOLATES of size 'N', where each element represents the number of chocolates in a packet. Your task is to distribute these chocolates among 'M'...read more
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Round duration - 60 Minutes
Round difficulty - Easy

Another On-site ( DS & Algo) interview.

Q1. 
Problem Statement: Minimize the Maximum
You are given an array of integers and an integer K. For each array element, you can adjust it by increasing or decreasing it by a value of K. Your goal is to minim...read more
Ans. 
Given an array of integers and an integer K, minimize the difference between the maximum and minimum elements after adjusting each element by +/- K.
• Sort the array in non-decreasing order.

• For each element, calculate the difference between the current element and the next element.

• Adjust the element by adding or subtracting K to minimize the difference.

• Return the minimum possible difference between the maximum and minimum...read more
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Round duration - 60 minutes
Round difficulty - Easy

On-site ( DS & Algo) interview.
Google mainly focuses on logic and how you are coming with a solution. It notes down each and every small mistake. Interviewers are really very helpful. They expect clear code with an optimal approach.

Q1. 
Farthest Distance From Lands Problem Statement
Given a binary square matrix 'ARR' with 'N' rows and 'N' columns, where '0' represents water and '1' represents land.
Determine the water cell whose distanc...read more
Ans. 
Find the water cell farthest from land in a binary matrix using Manhattan distance.
• Iterate through the matrix to find all land cells and water cells

• Calculate the Manhattan distance of each water cell to the nearest land cell

• Return the maximum distance found
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