10+ Pierburg India Interview Questions and Answers

Implement a function to sort an array of 0s and 1s in linear time complexity without using additional arrays.

• Iterate through the array and maintain two pointers, one for 0s and one for 1s.

• Swap elements at the two pointers to sort the array in place.

• Time complexity should be O(N) where N is the size of the array.

The problem involves finding the smallest set of vertices from which all nodes in a directed acyclic graph are reachable.

• Create a directed graph using the given edges.

• Perform a topological sort to find the vertices that can reach all other nodes.

• Output the smallest set of vertices in sorted order.

Flatten a multilevel sorted linked list while maintaining sorted order.

• Iterate through the linked list nodes and maintain a stack to keep track of child nodes.

• Merge the child nodes with the parent node in sorted order.

• Update the pointers to create a single level flattened linked list.

The task is to stack different types of rectangular 3D boxes to achieve the maximum possible height by following certain constraints.

• Sort the boxes based on their base dimensions in non-increasing order.

• Use dynamic programming to find the maximum height achievable by stacking the boxes.

• Consider all possible rotations of each box to maximize the height.

• Ensure that the base dimensions of the boxes below are strictly larger than the ones above.

• Handle multiple copies of the same ...read more

Given an integer, sum its digits until a single-digit number is obtained. Determine the final single-digit integer.

• Iteratively sum the digits of the integer until a single-digit number is obtained

• Output the final single-digit integer for each test case

• Handle multiple test cases efficiently

• Ensure the final value is less than 10

Implement a priority queue using a heap data structure by completing the provided class functions.

• Implement push(), pop(), getMaxElement(), and isEmpty() functions in the given class structure.

• Use a heap data structure to maintain the priority queue.

• Handle different types of queries (push, pop, getMaxElement, isEmpty) as per the given instructions.

• Ensure the functions return the correct values based on the type of query.

• Test the implementation with sample input and output pro...read more

Design a system for users to subscribe to topics and receive notifications for new messages.

• Create a user profile where they can select topics of interest to subscribe to.

• Implement a messaging system that sends notifications to users when new messages are posted related to their subscribed topics.

• Allow users to manage their subscriptions and preferences easily.

• Utilize a database to store user subscriptions and messages for efficient retrieval.

• Consider implementing push notifi...read more

Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.

• Abstract class can have constructors, fields, and methods, while interface cannot have any implementation.

• A class can only extend one abstract class, but can implement multiple interfaces.

• Abstract classes are used to define common characteristics of subclasses, while interfaces are used to define a contract for classes to implement.

• Example: Abstract class 'Shape' wit...read more

Binary Search halves the search space in each iteration, leading to a time complexity of O(Log n).

• Binary Search divides the array into two halves and compares the target value with the middle element.

• If the target value is less than the middle element, it searches in the left half; otherwise, it searches in the right half.

• This process continues until the target value is found or the subarray size becomes 0.

• Since each comparison reduces the search space by half, the time compl...read more

HashMap is a collection of key-value pairs, while HashSet is a collection of unique elements.

• HashMap allows duplicate values but keys must be unique

• HashSet does not allow duplicate elements

• HashMap uses key-value pairs for storing data, while HashSet only stores individual elements

• Example: HashMap<String, Integer> map = new HashMap<>(); HashSet<String> set = new HashSet<>();

Memory allocation in recursion involves creating a new stack frame for each recursive call.

• Each recursive call creates a new stack frame to store local variables and function parameters.

• Memory is allocated on the stack for each stack frame, which can lead to stack overflow if too many recursive calls are made.

• Once a recursive call returns, its stack frame is deallocated to free up memory.

• Example: Factorial function recursively calls itself to calculate the factorial of a numb...read more

Round Robin Algorithm is a CPU scheduling algorithm where each process is assigned a fixed time slice in a cyclic manner.

• Each process is given a small unit of time to execute, called a time slice or quantum.

• Once a process's time slice expires, it is moved to the end of the ready queue.

• The scheduler then moves to the next process in the queue and allocates it the CPU for its time slice.

• This continues until all processes have had a turn to execute.

• Example: If time slice is 10ms...read more

Virtual destructors are needed to ensure proper cleanup of resources in derived classes when using polymorphism.

• Virtual destructors are necessary to ensure that the destructor of the most derived class is called when deleting a base class pointer to a derived class object.

• Without virtual destructors, only the base class destructor would be called, leading to memory leaks and resource leaks in the derived class.

• Virtual destructors allow for proper cleanup of resources allocate...read more

A program to convert a given number into words.

• Use a switch statement or if-else conditions to handle different cases

• Break down the number into its individual digits and convert each digit into words

• Handle special cases like numbers between 10 and 20

• Consider adding a function to handle larger numbers with appropriate suffixes

An AVL tree is a self-balancing binary search tree where the heights of the two child subtrees of any node differ by at most one.

• AVL trees are named after their inventors Adelson-Velsky and Landis.

• They are used to maintain sorted data and ensure efficient search, insertion, and deletion operations.

• Balancing in AVL trees is achieved through rotations to maintain the height balance factor.

• Example: Inserting elements 1, 2, 3, 4, 5 into an AVL tree will result in a balanced tree ...read more

Threads are needed to allow a program to perform multiple tasks concurrently, improving performance and responsiveness.

• Threads allow for parallel execution of tasks, utilizing multiple CPU cores efficiently.

• Threads can improve responsiveness in applications by handling multiple tasks simultaneously.

• Threads are essential for implementing features like background processing, multitasking, and handling user input concurrently.

• Examples include web servers handling multiple client...read more