90+ 12th Wonder Research Interview Questions and Answers

The game is not fair.

• Player X has a higher chance of winning as they only need to get a consecutive HEAD, TAIL.

• Player Y needs to get a consecutive HEAD, HEAD which is less likely to occur.

• The probability of Player X winning is higher than Player Y winning.

The last ball that will be left is black.

• When you take out 2 black balls, you take another white ball.

• If you take 2 white balls, you take out 1 black ball.

• If balls are of different color, you take out another black ball.

• Since there are more black balls initially, the last ball will be black.

Design a website similar to bookmyshow.com for booking cinema tickets for a single location with multiple theatres.

• Design a user-friendly GUI with options for advance booking, user login, user registration, movie rating, and saving card details.

• Create relevant database tables to store information about movies, theatres, bookings, user details, and card details.

• Link the GUI to the database to enable data flow and retrieval.

• Implement features like advance booking, where users c...read more

The program prints the substring after a specified character has occurred a certain number of times in a given string.

• Iterate through the string to find the specified character.

• Keep track of the count of occurrences of the character.

• Once the count reaches the specified count, extract the substring after that position.

• Handle corner cases such as when the character is not in the string or when it doesn't occur the specified number of times.

To efficiently manage room bookings and prebookings in a hotel, a priority queue data structure can be implemented.

• A priority queue can be used to prioritize room bookings based on check-in dates.

• When a customer checks out, the room becomes available and can be assigned to the next customer in the priority queue.

• Prebookings can be stored separately and checked against the availability of rooms before assigning them to customers.

• The priority queue can be implemented using a bi...read more

Minimum number of times to turn all glasses upside down when 4 can be turned at a time.

• Turn over any four glasses, leaving one untouched.

• Repeat the above step until only one glass is left upside down.

• Finally, turn over the last glass to complete the task.

• Minimum number of turns required is 3.

Minimum 7 races required to find the top 3 fastest horses.

• Divide the 25 horses into 5 groups of 5 horses each.

• Conduct a race among the horses in each group to determine the fastest horse in each group.

• Take the top 2 horses from each group and conduct a race among them to determine the fastest horse overall.

• The winner of this race is the fastest horse.

• Now, take the second-place horse from the final race and the second-place horse from each group race.

• Conduct a race among these...read more

The minimum number of races required to find the top 3 among 25 horses is 7.

• Divide the 25 horses into 5 groups of 5 horses each.

• Race the 5 groups, which will give us the top 3 horses from each group.

• Now we have 15 horses remaining.

• Race the top 3 horses from each group, which will give us the top 3 horses overall.

• This requires a total of 7 races.

Print all possible paths from start to end in a linear way, moving either one or two steps right.

• Use dynamic programming to solve the problem

• Create a 2D array to store the number of paths to each position

• Start from the end position and work backwards

• At each position, calculate the number of paths by summing the number of paths from the next two positions

• Print all the paths by backtracking from the start position

Abstract classes in Java are classes that cannot be instantiated and are used as blueprints for other classes.

• Abstract classes cannot be instantiated, meaning you cannot create objects of an abstract class.

• Abstract classes can have both abstract and non-abstract methods.

• Interfaces in Java are similar to abstract classes, but they cannot have any method implementations.

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

• Abstract classes can hav...read more

The code inserts two numbers in a text file, ensuring that the second number is greater than the first and there is no overlap between entries.

• Read the existing entries from the text file

• Check if the new numbers satisfy the conditions

• If conditions are met, insert the new numbers into the file

• Otherwise, display an error message

Overloading is when multiple methods have the same name but different parameters. Overriding is when a subclass provides a different implementation of a method inherited from its superclass.

• Overloading allows a class to have multiple methods with the same name but different parameters.

• Overriding occurs when a subclass provides a different implementation of a method inherited from its superclass.

• Overloading is resolved at compile-time based on the method signature.

• Overriding i...read more

Undo operation (ctrl + z) is implemented by maintaining a stack of previous states.

• When a change is made, the current state is pushed onto the stack

• When undo is called, the top state is popped and applied

• Redo is implemented by maintaining a stack of undone states

• Some applications may also implement a limit on the number of undo/redo steps

• Undo/redo can be implemented at different levels (e.g. character, word, paragraph)

You can measure 4 liters by following these steps:

• Fill the 5 liters container completely

• Pour the 5 liters into the 3 liters container, leaving 2 liters in the 5 liters container

• Empty the 3 liters container

• Pour the remaining 2 liters from the 5 liters container into the 3 liters container

• Fill the 5 liters container again

• Pour 1 liter from the 5 liters container into the 3 liters container, which now has 3 liters

• The 5 liters container now has 4 liters

The algorithm for the upcoming semester project involves developing an application.

• Identify the requirements and objectives of the project

• Design the application architecture and user interface

• Implement the necessary algorithms and data structures

• Test and debug the application

• Optimize the performance and efficiency of the code

• Document the project for future reference

Code to find the middle element of a linked list

• Traverse the linked list with two pointers, one moving twice as fast as the other

• When the fast pointer reaches the end, the slow pointer will be at the middle element

• If the linked list has even number of elements, return the second middle element

Code to count the number of times '1' occurs from 1 to 999999

• Loop through all numbers from 1 to 999999

• Convert each number to a string and count the number of '1's in it

• Add the count to a running total

• Return the total count

The code prints the transpose of a given matrix.

• Iterate through each row and column of the matrix.

• Swap the elements at the current row and column with the elements at the current column and row.

• Print the transposed matrix.

Find the common ancestor of two given nodes in a tree

• Traverse the tree from the root node

• Check if both nodes are on the same side of the current node

• If not, return the current node as the common ancestor

• If yes, continue traversing down that side of the tree

The time complexity of 8 queens algorithm is O(n!).

• The algorithm checks all possible permutations of the queens on the board.

• The number of permutations is n! where n is the number of queens.

• For 8 queens, there are 8! = 40,320 possible permutations.

• The algorithm has to check each permutation to find a valid solution.

• Therefore, the time complexity is O(n!).

Arrange 4 coins to make maximum number of triangles

• Place 3 coins in a triangle formation and the fourth coin in the center to form 4 triangles

• Place 2 coins on top of each other and the other 2 coins on either side to form 2 triangles

• Place 2 coins in a line and the other 2 coins on either side to form 2 triangles

My favorite program is Visual Studio Code because of its user-friendly interface and extensive plugin library.

• User-friendly interface with customizable settings

• Extensive plugin library for various programming languages and tools

• Integrated terminal and debugging features

• Supports Git version control

• Frequent updates and improvements

• Free and open-source

• Examples: Python, JavaScript, HTML/CSS, Git

Arrange 10 coins in 4 rows of 4 coins each.

• Place 4 coins in a row and keep the remaining 6 aside.

• Place 3 coins from the remaining 6 in the next row and keep the remaining 3 aside.

• Place 2 coins from the remaining 3 in the third row and keep the remaining 1 aside.

• Place the last coin in the fourth row along with the remaining 1 coin from step 3.

• The final arrangement will have 4 rows with 4 coins each.

Count the frequency of each alphabet in a string.

• Iterate through the string and count the occurrence of each alphabet using a dictionary or array.

• Convert the string to lowercase or uppercase to avoid case sensitivity.

• Exclude non-alphabetic characters using regular expressions.

• Consider using built-in functions or libraries for efficiency.

• Handle edge cases such as empty strings or strings with no alphabetic characters.

Count the number of palindromes in a given string.

• A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward.

• Iterate through the string and check if each substring is a palindrome.

• Use two pointers, one at the beginning and one at the end of the substring, and move them towards each other until they meet in the middle.

• If the substring is a palindrome, increment the count.

• Consider both even and odd length palindromes.

Find the fifth largest element in a linked list

• Traverse the linked list and store the elements in an array

• Sort the array in descending order

• Return the fifth element in the sorted array

Multitasking is the ability of an operating system to run multiple tasks concurrently while multiprogramming is the ability to run multiple programs concurrently.

• Multitasking allows multiple tasks to run concurrently on a single processor system.

• Multiprogramming allows multiple programs to run concurrently on a single processor system.

• Multitasking is achieved through time-sharing, where the processor switches between tasks at a very high speed.

• Multiprogramming is achieved thr...read more

To find the maximum salary in emp table, use the MAX function on the salary column.

• Use the MAX function in SQL to find the highest value in a column

• Specify the column name after the MAX function, in this case 'salary'

• Example: SELECT MAX(salary) FROM emp

• This will return the highest salary value in the emp table

ER diagrams are used to visualize and design relational databases.

• ER diagrams show the relationships between entities in a database

• They help in identifying the attributes of each entity

• They aid in designing the structure of a database

• ER diagrams are commonly used in software development

Circular doubly linked list is a data structure where each node has a reference to both the next and previous nodes, forming a circular loop.

• Create a Node class with data, next, and prev pointers

• Implement operations like insert, delete, search, and display

• Ensure the last node's next pointer points to the first node and the first node's prev pointer points to the last node

Searching and sorting algorithms are essential in programming for efficiently organizing and retrieving data.

• Searching algorithms: linear search, binary search, depth-first search, breadth-first search

• Sorting algorithms: bubble sort, selection sort, insertion sort, merge sort, quick sort

• Examples: Searching for a specific item in a list, sorting a list of numbers in ascending order

Towers of Hanoi is a classic problem of moving disks from one peg to another with specific rules.

• The problem involves three pegs and a number of disks of different sizes.

• The goal is to move all the disks from the first peg to the third peg, while following the rules.

• The rules are: only one disk can be moved at a time, a larger disk cannot be placed on top of a smaller disk, and all disks must be moved to the third peg.

• The solution can be implemented recursively.

• Example code: ...read more

Explanation of three normalizations with examples

• First Normal Form (1NF): Eliminate duplicate data and create separate tables for related data

• Example: A table with customer information and their orders should be split into two tables

• Second Normal Form (2NF): Ensure non-key attributes are dependent on the primary key

• Example: A table with customer information and their orders should have separate tables for customer and order details

• Third Normal Form (3NF): Eliminate transitive...read more

Find duplicates in an array

• Iterate through the array and compare each element with the rest of the elements

• Use a hash table to keep track of the frequency of each element

• Sort the array and compare adjacent elements

• Use a set to keep track of unique elements and add duplicates to another set

Semaphore allows multiple threads to access shared resources at the same time, while mutex allows only one thread at a time.

• Semaphore is used to control access to a resource with limited capacity, like a printer or database connection pool.

• Mutex is used to protect a shared resource from simultaneous access, like a critical section of code.

• Semaphore can have a count greater than 1, allowing multiple threads to access the resource simultaneously.

• Mutex has a binary state, either...read more

Implementing queue using linked lists

• Create a Node class with data and next pointer

• Create a Queue class with head and tail pointers

• Enqueue by adding a new node at the tail and dequeue by removing the head node

• Check for empty queue by checking if head is null

The minimum area of a square that contains all given points is the square of the maximum distance between any two points.

• Calculate the distance between all pairs of points

• Find the maximum distance

• Square the maximum distance to get the minimum area of the square

Designing a hashmap from scratch

• A hashmap is a data structure that allows for efficient key-value pair storage and retrieval

• It typically uses an array and a hashing function to map keys to array indices

• Collision handling techniques like chaining or open addressing may be used

• Operations like insert, delete, and search can be implemented using the hashmap

• Example: Designing a hashmap to store student records with their roll numbers as keys

Find the largest element in a window of size K in an array.

• Iterate through the array and maintain a deque to store the indices of elements in decreasing order.

• Remove indices from the front of the deque that are outside the current window.

• The front of the deque will always have the index of the largest element in the current window.

Merge two sorted linked lists

• Create a new linked list to store the merged list

• Compare the first nodes of both lists and add the smaller one to the new list

• Move the pointer of the added node to the next node

• Repeat until one of the lists is empty, then add the remaining nodes to the new list

8 Queens Algorithm is a backtracking algorithm to place 8 queens on a chessboard without attacking each other.

• The algorithm places one queen in each column, starting from the leftmost column.

• If a queen can be placed in a row without attacking another queen, it is placed there.

• If no such row exists, the algorithm backtracks to the previous column and tries a different row.

• The algorithm continues until all 8 queens are placed on the board without attacking each other.

• The algori...read more

Interfaces in Java define a contract for classes to implement certain methods.

• Interfaces are like a blueprint for classes to follow

• They can contain method signatures but no implementation

• Classes can implement multiple interfaces

• Interfaces can extend other interfaces

• Example: Comparable interface for sorting objects

Find the maximum length of a subarray with a given sum in an array.

• Use a hashmap to store the running sum and its corresponding index.

• Iterate through the array and update the hashmap with the running sum.

• Check if the difference between the current sum and the target sum exists in the hashmap to find the subarray length.

Traversing a singly linked list involves iterating through each node starting from the head node.

• Start at the head node

• Iterate through each node by following the 'next' pointer

• Stop when reaching the end of the list (next pointer is null)

Heap sort is a comparison-based sorting algorithm that uses a binary heap data structure.

• It divides the input into a sorted and an unsorted region.

• It repeatedly extracts the largest element from the unsorted region and inserts it into the sorted region.

• It has a worst-case and average-case time complexity of O(n log n).

Reverse a string

• Use a loop to iterate through the string and append each character to a new string in reverse order

• Alternatively, use the built-in reverse() method for strings in some programming languages

Use iterative approach to traverse both linked lists and sum corresponding nodes while keeping track of carry.

• Iterate through both linked lists simultaneously

• Sum corresponding nodes and carry from previous sum

• Create a new linked list to store the sum

Design a hotel booking system.

• Create a database to store hotel information, room availability, and bookings.

• Develop a user interface for customers to search and book hotels.

• Implement a payment gateway for secure transactions.

• Include features like room selection, date selection, and guest information.

• Consider implementing a rating and review system for hotels.

• Ensure the system can handle concurrent bookings and prevent double bookings.

SQL query using joins

• Use JOIN keyword to combine rows from two or more tables based on a related column between them

• Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column

Merge two sorted arrays into a single sorted array

• Create a new array to store the merged result

• Use two pointers to iterate through both arrays and compare elements

• Add the smaller element to the new array and move the pointer for that array

Shallow copy only copies the references of objects, while deep copy creates new copies of objects.

• Shallow copy creates a new object but does not create copies of nested objects.

• Deep copy creates new copies of all nested objects.

• Shallow copy is faster and more memory efficient, but changes to nested objects affect both copies.

• Deep copy is slower and uses more memory, but changes to nested objects do not affect the original object.

Design a Tic Tac Toe game

• Create a 3x3 grid to represent the game board

• Allow two players to take turns marking X and O on the grid

• Check for win conditions after each move to determine the winner

• Handle tie game if all spaces are filled without a winner

Calculate the area of a shape using coordinates

• Determine the type of shape (e.g. rectangle, triangle, circle)

• Use the appropriate formula for the shape to calculate the area

• Input the coordinates into the formula to get the area