GoFrugal Technologies QA Interview Questions, Process, and Tips

Round duration - 60 minutes
Round difficulty - Medium

This was a written round. Proper code with correct syntax to be written on paper.
There were 4 questions to be solved in 1 hour. Some questions needed test cases and time complexity to be answered as well.

Q1. 
Add Two Numbers as Linked Lists
You are given two singly linked lists, where each list represents a positive number without any leading zeros.
Your task is to add these two numbers and return the sum as ...read more
Ans. 
Add two numbers represented as linked lists and return the sum as a linked list.
• Traverse both linked lists simultaneously while keeping track of carry from previous sum

• Handle cases where one linked list is longer than the other by padding with zeros

• Create a new linked list to store the sum of the two numbers
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Q2. 
Minimum Number Of Operations To Reach X Problem Statement
Given an array ARR of 'N' integers and an integer 'X', determine the minimum number of operations required to make the sum of removed elements fro...read more
Ans. 
Given an array of integers and a target sum, find the minimum number of operations to make the sum of removed elements equal to the target.
• Iterate from both ends of the array, removing elements until the sum matches the target

• Use a two-pointer approach to efficiently find the minimum number of operations

• If achieving the target sum is not possible, return -1
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Q3. 
Product Of Array Except Self Problem Statement
You are provided with an integer array ARR of size N. You need to return an array PRODUCT such that PRODUCT[i] equals the product of all the elements of ARR ...read more
Ans. 
The problem requires returning an array where each element is the product of all elements in the input array except itself.
• Iterate through the array twice to calculate the product of all elements to the left and right of each element.

• Use two arrays to store the products to the left and right of each element.

• Multiply the corresponding elements from the left and right arrays to get the final product array.

• Handle integer ...read more
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Q4. 
Sort a Stack Problem Statement
You are provided with a stack consisting of 'N' integers. The goal is to sort this stack in descending order by utilizing recursion.
Allowed Stack Operations:
is_empty(S) ...read more
Ans. 
Sort a stack in descending order using recursion without using loop constructs.
• Implement a recursive function to sort the stack in descending order.

• Use the provided stack operations to manipulate the stack.

• Recursively pop elements from the stack, sort them, and push them back in descending order.

• Handle base cases such as an empty stack or a single element stack.

• Ensure the stack is sorted in descending order after the r...read more
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Round duration - 60 minutes
Round difficulty - Easy

General questions based on resume, was asked to explain my internship project.
He asked questions on my written round. Asked me to find the bug in my code for 1st problem. He was extremely happy with me when I gave the correct answer.
He asked me for the code for the last problem since I hadn’t solved it.
Asked to reverse linked list using recursion, since I said I did by iteration earlier.
He had written code of second problem, I had to find bugs in it.
Discussion on quality engineering and developer profiles.

Q1. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. 
Reverse a singly linked list of integers and return the head of the reversed linked list.
• Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

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

• Update the head of the reversed linked list as the last node encountered during the reversal process.
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Round duration - 60 minutes
Round difficulty - Medium

Technical round that lasted for around 60 minutes. The interviewer asked questions on data structures and OOPS concepts.

Q1. 
Problem: Permutations of a String
Given a string STR consisting of lowercase English letters, your task is to return all permutations of the given string in lexicographically increasing order.
Explanatio...read more
Ans. 
Return all permutations of a given string in lexicographically increasing order.
• Generate all permutations of the given string using backtracking.

• Sort the permutations in lexicographical order.

• Print the sorted permutations separated by space.
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Q2. 
Greatest Common Divisor Problem Statement
You are tasked with finding the greatest common divisor (GCD) of two given numbers 'X' and 'Y'. The GCD is defined as the largest integer that divides both of the...read more
Ans. 
Find the greatest common divisor (GCD) of two given numbers 'X' and 'Y'.
• Implement a function to calculate GCD using Euclidean algorithm

• Iteratively find the remainder of X divided by Y until Y becomes 0

• The last non-zero remainder is the GCD of X and Y
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Q3. What are the differences between C, C++, and Java?
Ans. 
C is a procedural language, C++ is an object-oriented language, and Java is a platform-independent language.
• C is a procedural programming language, while C++ supports both procedural and object-oriented programming.

• C++ is an extension of C with additional features like classes and inheritance.

• Java is a platform-independent language that runs on a virtual machine and uses automatic memory management.

• C is closer to the h...read more
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Q4. What is the purpose of the virtual keyword in C++?
Ans. 
The virtual keyword in C++ is used to declare a member function in a base class that can be overridden in derived classes.
• Virtual functions allow for dynamic polymorphism in C++ by enabling late binding.

• Virtual functions are declared in the base class with the 'virtual' keyword and can be overridden in derived classes.

• When a derived class overrides a virtual function, the function in the derived class is called instead...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical round that lasted for around 60 minutes. The interviewer asked questions on data structures and question related to cloud computing(cloud computing was listed on my resume) .

Q1. 
LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key) - Return the value of the key if it exists in the cache; otherw...read more
Ans. 
Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.
• Implement a doubly linked list to keep track of the order of keys based on their recent usage.

• Use a hashmap to store key-value pairs for quick access and update.

• When capacity is reached, evict the least recently used item before inserting a new item.

• Update the order of keys in the linked list whenever a...read more
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Q2. 
Problem Statement: Delete Node In A Linked List
Given a singly linked list of integers and a reference to a node, your task is to delete that specific node from the linked list. Each node in the linked li...read more
Ans. 
Delete a specific node from a singly linked list given the reference to the node.
• Traverse the linked list to find the node to be deleted.

• Update the pointers to skip over the node to be deleted.

• Print the modified linked list after deletion.
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Round duration - 60 minutes
Round difficulty - Easy

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

Q1. 
Insertion Sort in a Linked List
Given a singly linked list with 'N' nodes containing integer values, your task is to sort the list using insertion sort and output the sorted list.
Insertion Sort is an al...read more
Ans. 
Implement insertion sort algorithm on a singly linked list.
• Traverse the linked list and for each node, find its correct position in the sorted list.

• Keep track of the current node and the previous node to perform the insertion.

• Repeat this process until all nodes are sorted in the linked list.

• Ensure to handle edge cases like empty list or list with only one node.
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Q2. 
Find Duplicates in an Array
Given an array ARR of size 'N', where each integer is in the range from 0 to N - 1, identify all elements that appear more than once.
Return the duplicate elements in any orde...read more
Ans. 
Find duplicates in an array of integers within a specified range.
• Iterate through the array and keep track of the count of each element using a hashmap.

• Return elements with count greater than 1 as duplicates.

• Time complexity can be optimized to O(N) using a set to store duplicates.
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Round duration - 40 minutes
Round difficulty - Easy

The Interviewer asked me questions to know more about me. He also asked a puzzle.

Q1. You have a racetrack with 25 horses. What is the fastest way to determine the top 3 fastest horses, given that you can only race 5 horses at a time?
Ans. 
To determine the top 3 fastest horses out of 25, race horses in groups of 5 and keep track of the fastest horses in each race.
• Divide the 25 horses into 5 groups of 5 horses each.

• Race all 5 horses in each group, keeping track of the top 3 fastest horses in each race.

• After 5 races, you will have the top 3 fastest horses from each group.

• Race the top 3 horses from each group in a final race to determine the overall top 3 f
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Round duration - 60 minutes
Round difficulty - Medium

The interviewer grilled me completely in Java.

Q1. What is the AtomicInteger class in Java?
Ans. 
AtomicInteger is a class in Java that provides atomic operations on integers.
• It is used for operations that need to be performed atomically, without interference from other threads.

• Common methods include get(), set(), incrementAndGet(), decrementAndGet(), etc.

• Example: AtomicInteger count = new AtomicInteger(0); count.incrementAndGet();
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Q2. Can you explain the Collection Hierarchy in Java?
Ans. 
Collection Hierarchy in Java represents the relationship between various collection interfaces and classes.
• Collection interface is the root interface in the Collection Hierarchy.

• List and Set interfaces extend the Collection interface.

• Map interface is not a subtype of Collection interface.

• ArrayList, LinkedList, HashSet, and TreeSet are some of the classes that implement the Collection interfaces.

• HashMap and TreeMap are
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Q3. What is the internal functioning of a hashmap in Java?
Ans. 
HashMap in Java is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values.
• HashMap uses an array of buckets to store key-value pairs.

• The key is hashed to determine the index in the array where the value will be stored.

• In case of hash collisions, a linked list or a balanced tree is used to store multiple values at the same index.

• HashMap allows null keys and values.

• Example: HashMap<...read more
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Q4. What is the difference between fail-fast and fail-safe iterators in Java?
Ans. 
Fail-fast iterators throw ConcurrentModificationException if the collection is modified while iterating. Fail-safe iterators do not throw exceptions and operate on a cloned copy of the collection.
• Fail-fast iterators throw ConcurrentModificationException if the collection is modified while iterating.

• Fail-safe iterators do not throw exceptions and operate on a cloned copy of the collection.

• Fail-fast iterators are used in...read more
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Q5. What are the different ways you can traverse over a map in Java?
Ans. 
Different ways to traverse over a map in Java include using keySet(), entrySet(), and forEach() method.
• Use keySet() method to iterate over keys in the map

• Use entrySet() method to iterate over key-value pairs in the map

• Use forEach() method to iterate over key-value pairs in the map
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Round duration - 60 minues
Round difficulty - Medium

Questions based on data structures, OS and system design were asked in this round.

Q1. 
Median of Two Sorted Arrays
Given two sorted arrays A and B of sizes N and M, find the median of the merged array formed by combining arrays A and B. If the total number of elements, N + M, is even, the m...read more
Ans. 
Find the median of two sorted arrays by merging them and calculating the median of the combined array.
• Merge the two sorted arrays into one sorted array.

• Calculate the median of the merged array based on the total number of elements.

• If the total number of elements is even, take the mean of the two middle elements as the median.
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Q2. Design a bus seat booking system.
Ans. 
Design a bus seat booking system.
• Use a database to store seat availability and bookings

• Implement a user interface for customers to select and book seats

• Consider implementing a payment system for reservations

• Allow for seat selection based on preferences such as window or aisle
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Q3. What is fragmentation in operating systems?
Ans. 
Fragmentation in operating systems is the phenomenon where memory or disk space is divided into small chunks over time, leading to inefficient use of resources.
• Fragmentation can occur in both memory (memory fragmentation) and disk space (disk fragmentation).

• External fragmentation happens when free memory or disk space is broken into small pieces, making it difficult to allocate large contiguous blocks of memory or disk...read more
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Q4. What can you tell me about memory management in operating systems?
Ans. 
Memory management in operating systems involves allocation, deallocation, and optimization of memory usage.
• Memory management is crucial for efficient utilization of system resources.

• Operating systems use techniques like paging, segmentation, and virtual memory to manage memory.

• Memory management also involves handling memory leaks, fragmentation, and ensuring data integrity.

• Examples include malloc() and free() functions
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Round duration - 60 minutes
Round difficulty - Hard

10 MCQs and 3 programming questions are given.
MCQs included questions asking the outputs of code snippets, algorithmic complexities.
Programming problems are tough.
I was able to solve only 1 problem completely and 1 partially.
Partial score is given for passing some test cases.
Tips: For programming problems code any solution(even brute force) if you are not able to come up with exact solution

Q1. 
LCA of Binary Tree Problem Statement
You are given a binary tree consisting of distinct integers and two nodes, X and Y. Your task is to find and return the Lowest Common Ancestor (LCA) of these two nodes...read more
Ans. 
Find the Lowest Common Ancestor (LCA) of two nodes in a binary tree.
• Traverse the binary tree to find the paths from the root to nodes X and Y.

• Compare the paths to find the last common node, which is the LCA.

• Handle cases where one node is an ancestor of the other.

• Consider edge cases like when X or Y is the root node.

• Implement a recursive or iterative solution to find the LCA efficiently.
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Q2. 
Stack with getMin Operation
Create a stack data structure that supports not only the usual push and pop operations but also getMin(), which retrieves the minimum element, all in O(1) time complexity witho...read more
Ans. 
Implement a stack with getMin operation in O(1) time complexity without using extra space.
• Use two stacks - one to store the actual elements and another to store the minimum values encountered so far.

• When pushing an element, check if it is smaller than the current minimum and if so, push it onto the minimum stack.

• When popping an element, check if it is the current minimum and if so, pop from the minimum stack as well.

• Fo...read more
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Round duration - 60 minutes
Round difficulty - Easy

This was a technical interview round. I was able to solve all questions.

Q1. 
Count Pairs with Given Sum
Given an integer array/list arr and an integer 'Sum', determine the total number of unique pairs in the array whose elements sum up to the given 'Sum'.
Input:
The first line c...read more
Ans. 
Count the total number of unique pairs in an array whose elements sum up to a given value.
• Iterate through the array and for each element, check if the complement (Sum - current element) exists in a hash set.

• If the complement exists, increment the count of pairs and remove the complement from the set to avoid duplicates.

• Return the total count of pairs at the end.
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Q2. Can you explain all 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 a class to inherit pr...read more
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Round duration - 60 minutes
Round difficulty - Hard

I couldn't answer 3rd and 4th questions properly but gave some suboptimal solutions.
Tips: Answer multiple solutions trading off time and space complexities

Q1. Calculate the definite integral of a function within the limits a to b.
Ans. 
Definite integral of a function within given limits a to b.
• Use the definite integral formula: ∫[a, b] f(x) dx = F(b) - F(a), where F(x) is the antiderivative of f(x).

• Calculate the antiderivative of the function and then evaluate it at the upper and lower limits.

• Make sure to check for any discontinuities or singularities within the interval.

• Example: Calculate ∫[0, 2] x^2 dx = (1/3)x^3 |[0, 2] = (1/3)(2^3) - (1/3)(0^3) =
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Q2. 
Closest Distance Pair Problem Statement
Given an array containing 'N' points in a 2D plane, determine the minimum distance between the closest pair of points.
Note:
Distance between two points (x1, y1) ...read more
Ans. 
The problem involves finding the minimum distance between the closest pair of points in a 2D plane.
• Iterate through all pairs of points and calculate the distance between them using the given formula.

• Keep track of the minimum distance found so far.

• Optimize the solution by using techniques like sorting the points based on x or y coordinates.
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Q3. How would you design a website that displays the top 1000 products with product ratings that update every second?
Ans. 
Design a website to display top 1000 products with real-time ratings.
• Utilize a backend server to fetch and update product ratings every second.

• Implement a front-end framework like React to display the products and ratings dynamically.

• Use a database to store and retrieve product information efficiently.

• Consider implementing caching mechanisms to reduce server load.

• Optimize the website for performance to handle frequent
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Round duration - 60 minutes
Round difficulty - Medium

It comprised of general aptitude questions and two coding questions. It was an offline test.

Q1. 
N Queens Problem
Given an integer N, find all possible placements of N queens on an N x N chessboard such that no two queens threaten each other.
Explanation:
A queen can attack another queen if they ar...read more
Ans. 
The N Queens Problem involves finding all possible placements of N queens on an N x N chessboard without threatening each other.
• Use backtracking algorithm to explore all possible configurations.

• Keep track of rows, columns, and diagonals to ensure queens do not threaten each other.

• Generate all valid configurations and print them out.
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Q2. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an array of 0s, 1s, and 2s in linear time complexity using a single scan.
• Use three pointers to keep track of the positions of 0s, 1s, and 2s in the array.

• Iterate through the array and swap elements based on their values and the pointers.

• After a single scan, the array will be sorted in-place with 0s, 1s, and 2s in order.
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Round duration - 60 minutes
Round difficulty - Easy

The interviewer started by having a look at my CV. He asked for a firm technical introduction. He asked question about my projects. As I have had my intern from a very good place, he appeared impressed from the very start. After having a technical discussion about my CV, he gave me 2 questions to code.

Q1. 
Detect the First Node of the Loop in a Singly Linked List
You are provided with a singly linked list that may contain a cycle. Your task is to return the node where the cycle begins, if such a cycle exist...read more
Ans. 
To detect the first node of a loop in a singly linked list, we can use Floyd's Cycle Detection Algorithm.
• Use Floyd's Cycle Detection Algorithm to detect the cycle in the linked list.

• Once the cycle is detected, find the starting node of the cycle using two pointers approach.

• The first pointer moves one step at a time while the second pointer moves two steps at a time until they meet at the starting node of the cycle.
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Q2. 
Word Presence in Sentence
Determine if a given word 'W' is present in the sentence 'S' as a complete word. The word should not merely be a substring of another word.
Input:
The first line contains an in...read more
Ans. 
Check if a given word is present in a sentence as a complete word.
• Split the sentence into words using spaces as delimiter.

• Check if the given word matches any of the words in the sentence.

• Ensure the word is not just a substring of another word in the sentence.
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Round duration - 60 minutes
Round difficulty - Easy

The interviewer was a young guy. He too had a look at my CV and appeared impressed. He discussed in detail about the two major projects done during my internship. He sat smiling at me with a friendly look and said that yes you have had actually done a lot of work. In the end for formality sake he gave me one question to code

Q1. 
Inorder Successor in a Binary Tree
Find the inorder successor of a given node in a binary tree. The inorder successor is the node that appears immediately after the given node during an inorder traversal....read more
Ans. 
Find the inorder successor of a given node in a binary tree.
• Perform an inorder traversal of the binary tree to find the successor node

• If the given node has a right child, the successor is the leftmost node in the right subtree

• If the given node does not have a right child, backtrack to find the ancestor whose left child is the given node
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Round duration - 45 minutes
Round difficulty - Easy

This was supposed to be the HR round but out of surprise the interviewer started by giving me a question to code.
After I approached this question with the right solution he just asked about my family. After that he said to wait.
After half an hour the results were announced. A total of three students were hired and I was amongst one of them.

Q1. 
Generate All Parentheses Combinations
Given an integer N, your task is to create all possible valid parentheses configurations that are well-formed using N pairs. A sequence of parentheses is considered w...read more
Ans. 
Generate all valid parentheses combinations for N pairs.
• Use backtracking to generate all possible combinations of parentheses.

• Keep track of the number of open and close parentheses used.

• Add '(' if there are remaining open parentheses, and add ')' if there are remaining close parentheses.

• Stop when the length of the generated string is 2*N.
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