60+ Walker Digital Table Systems Interview Questions and Answers

The task is to delete the middle node of a singly linked list of integers.

• If the linked list is empty or has only one node, there is no middle node to delete.

• To delete the middle node, we need to find the middle node and update the pointers of the previous and next nodes.

• To find the middle node in one traversal, we can use two pointers - a slow pointer and a fast pointer.

• The slow pointer moves one node at a time, while the fast pointer moves two nodes at a time.

• When the fast ...read more

The task is to find the length of the shortest contiguous subarray that needs to be sorted in order to sort the entire array.

• Iterate through the array from left to right and find the first element that is out of order.

• Iterate through the array from right to left and find the first element that is out of order.

• Find the minimum and maximum elements within the subarray defined by the above two elements.

• Expand the subarray to include any additional elements that are out of order ...read more

This is a problem where a sorted array is rotated and we need to search for given numbers in the array.

• The array is rotated clockwise by an unknown amount.

• We need to perform binary search to find the index of the given numbers.

• If the number is found, return its index. Otherwise, return -1.

• The time complexity of the solution should be O(logN).

The question asks to implement quick sort algorithm to sort an array of integers in ascending order.

• Quick sort is a divide and conquer algorithm

• Choose a pivot point and partition the array into two parts

• Recursively sort the left and right parts of the array

• Implement the quick sort algorithm to sort the given array

The task is to swap each even bit of an integer with its adjacent bit on the right in its binary representation.

• Convert the given integer to its binary representation

• Iterate through the binary representation and swap each even bit with its adjacent bit on the right

• Convert the modified binary representation back to an integer

• Print the resulting integer

The task is to find the lowest common ancestor (LCA) of two given nodes in a binary search tree (BST).

• The LCA is the lowest node that has both given nodes as descendants.

• In a BST, the left subtree of a node contains only nodes with data less than the node's data, and the right subtree contains only nodes with data greater than the node's data.

• Start from the root node and compare it with the given nodes. If both nodes are smaller than the current node, move to the left subtree...read more

The task is to merge two sorted linked lists into a single sorted linked list.

• Create a new linked list to store the merged list

• Compare the values of the nodes from both lists and add the smaller value to the new list

• Move the pointer of the list with the smaller value to the next node

• Repeat the comparison and addition until one of the lists is empty

• Add the remaining nodes from the non-empty list to the new list

• Return the head of the new list

The task is to return the spiral path of a given matrix.

• Iterate through the matrix in a spiral pattern, starting from the outermost layer and moving towards the center.

• Keep track of the current row, column, and the boundaries of the remaining unvisited matrix.

• Print the elements in the spiral path as you traverse the matrix.

To speed up multiplication of small integers in an array, we can use bitwise operations and parallel processing.

• Use bitwise operations like shifting and ANDing to perform multiplication faster.

• Divide the array into smaller chunks and perform multiplication in parallel using multi-threading or SIMD instructions.

• Use lookup tables for frequently used values to avoid repeated calculations.

• Use compiler optimizations like loop unrolling and vectorization.

• Consider using specialized ...read more

i is stored in global data segment, j is stored in stack, k is stored in heap.

• i is a global variable and is stored in the global data segment

• j is a local variable and is stored in the stack

• k is a pointer variable and is stored in the stack, while the memory it points to is allocated on the heap using malloc()

The Diamond Problem is a conflict that occurs when a class inherits from two classes that have a common base class.

• The Diamond Problem arises in multiple inheritance.

• It occurs when a class inherits from two classes that have a common base class.

• This leads to ambiguity in accessing the common base class members.

• To fix the Diamond Problem, virtual inheritance is used.

• Virtual inheritance ensures that only one instance of the common base class is inherited.

Virtual destructors in C++ are used to ensure that the correct destructor is called when deleting an object through a pointer to its base class.

• Virtual destructors are declared in the base class and are used when deleting an object through a pointer to the base class.

• They allow proper destruction of derived class objects.

• Without virtual destructors, only the base class destructor would be called, leading to memory leaks and undefined behavior.

• Virtual destructors are necessary...read more

Use a hash table to store the words and check for existence in constant time.

• Create a hash table with the words as keys and a boolean value as the value.

• For each new word, check if it exists in the hash table. If it does, it has appeared before. If not, add it to the hash table.

• Alternatively, use a set data structure to store only the unique words and check for existence in the set.

Semaphores are synchronization primitives used in operating systems to control access to shared resources.

• Binary semaphore: Can take only two values, 0 and 1. Used for mutual exclusion.

• Counting semaphore: Can take any non-negative integer value. Used for resource allocation.

• Mutex semaphore: A binary semaphore used for mutual exclusion.

• Named semaphore: A semaphore that can be accessed by multiple processes.

• Unnamed semaphore: A semaphore that can only be accessed by threads wit...read more

To determine if a point is inside a polygon, use the ray casting algorithm.

• Create a line from the point to a point outside the polygon

• Count the number of times the line intersects with the polygon edges

• If the count is odd, the point is inside the polygon; otherwise, it is outside

To remove unnecessary parenthesis from an expression, we need to apply a set of rules to identify and eliminate them.

• Identify and remove parenthesis around single variables or constants

• Identify and remove parenthesis around expressions with only one operator

• Identify and remove parenthesis around expressions with operators of equal precedence

• Identify and remove parenthesis around expressions with operators of different precedence

• Apply the rules recursively until no more unnece...read more

Find the maximum product of three integers in an array.

• Sort the array in descending order.

• Check the product of the first three numbers and the product of the first and last two numbers.

• Return the maximum of the two products.

Find length of longest consecutive sub array forming an AP from given array of integers.

• Sort the array in ascending order

• Iterate through the array and find the longest consecutive sub array forming an AP

• Use a variable to keep track of the length of the current consecutive sub array forming an AP

• Use another variable to keep track of the length of the longest consecutive sub array forming an AP seen so far

The four storage classes in C are auto, register, static, and extern.

• Auto: default storage class for all local variables

• Register: used to define local variables that should be stored in a register instead of RAM

• Static: used to define local variables that retain their value between function calls

• Extern: used to declare a global variable that is defined in another file

Static variables are allocated memory in the data segment of the program's memory space.

• Static variables have a fixed memory location throughout the program's execution.

• They are initialized to zero by default.

• If initialized explicitly, they are stored in the data segment.

• Static variables can be accessed by any function in the program.

To find a new array where each element is the product of all elements in the original array except the element at that index without using division operator.

• Iterate through the array and calculate the product of all elements to the left of the current index for each element.

• Iterate through the array in reverse and calculate the product of all elements to the right of the current index for each element.

• Multiply the results from the two steps above to get the final array.

Search for an element in a sorted 2D array and return its index if found

• Start from the top right corner and compare the target element with the current element

• If the target is smaller, move left; if larger, move down

• Repeat until the element is found or all elements are checked

Given an integer, determine which byte is zero.

• Convert the integer to a byte array using bitwise operations.

• Iterate through the byte array and check for a zero value.

• Return the index of the zero byte.

• Consider endianness when converting to byte array.

Find the Next Greatest Element to the right for each element in an array of strings.

• Iterate through the array from right to left

• Use a stack to keep track of elements

• Pop elements from stack until a greater element is found

• If no greater element is found, assign -1

• Return the result array

To check endianness, create a 4-byte integer with a known value and check the byte order.

• Create a 4-byte integer with a known value

• Check the value of the first byte to determine endianness

• If the first byte is the least significant, the machine is little endian

• If the first byte is the most significant, the machine is big endian

Finding space and time complexity of a recursive function.

• Space complexity is the amount of memory used by the function.

• Time complexity is the amount of time taken by the function to execute.

• Recursive functions have higher space complexity due to the call stack.

• Time complexity can be calculated using Big O notation.

• Examples of recursive functions include factorial and Fibonacci sequence.

Return all root to leaf node paths in a binary tree with row, col and value.

• Traverse the binary tree recursively and keep track of the current path.

• When a leaf node is reached, add the path to the result array.

• Include row, col and value of each node in the path.

• Use an array of strings to store the paths.

Static objects can be used to print something before main() execution.

• Static objects are initialized before main() execution

• They can be used to print something before main()

• Example: static int x = printf("Hello World!");

• Output: Hello World! will be printed before main() execution

OOPS stands for Object-Oriented Programming. It is a programming paradigm that uses objects and classes for code organization and reusability.

• OOPS allows for better code organization and reusability through the use of classes and objects.

• Encapsulation, inheritance, and polymorphism are key principles of OOPS.

• Examples of OOPS languages include Java, C++, and Python.

DBMS stands for Database Management System. It is used to manage and organize data efficiently. It provides data security, integrity, and easy access.

• DBMS helps in organizing and managing data efficiently.

• It ensures data security and integrity by providing access control and data encryption.

• DBMS allows for easy retrieval and manipulation of data through query languages like SQL.

• Examples of DBMS include MySQL, Oracle, and Microsoft SQL Server.

DSA stands for Data Structures and Algorithms. Web development is the process of creating websites and web applications.

• DSA involves organizing and storing data efficiently for quick access and manipulation

• Web development includes front-end (client-side) and back-end (server-side) development

• Examples of DSA include arrays, linked lists, and sorting algorithms

• Examples of web development technologies include HTML, CSS, JavaScript, and frameworks like React and Node.js

Design a data structure for excel spreadsheet

• Use a 2D array to store cell values

• Implement formulas using a stack

• Include formatting options for cells

Merge two sorted linked lists using recursion

• Create a recursive function that compares the first nodes of both lists

• Set the smaller node as the head of the merged list and call the function again with the next node of the smaller list

• Base case: if one list is empty, return the other list

• Return the merged list

To get max value from a stack in O(1), maintain a separate stack to keep track of maximum values.

• Create a separate stack to keep track of maximum values

• Push the maximum value onto the stack whenever a new maximum is encountered

• Pop the maximum value stack whenever the top element of the main stack is popped

• Return the top element of the maximum value stack to get the maximum value in O(1)

Sieve of Eratosthenes is an algorithm for finding all prime numbers up to a given limit.

• Algorithm eliminates multiples of each prime number starting from 2

• Remaining numbers are prime

• Example: Finding prime numbers up to 30 - 2, 3, 5, 7, 11, 13, 17, 19, 23, 29

To get max element from a queue in O(1) time complexity

• Maintain a separate variable to keep track of the maximum element in the queue

• Update the maximum element variable whenever a new element is added or removed from the queue

• Return the maximum element variable when getMax() function is called

Insertion sort and quicksort are sorting algorithms used to sort arrays of data.

• Insertion sort: iterates through the array and inserts each element into its proper position.

• Quicksort: selects a pivot element and partitions the array into two sub-arrays, one with elements less than the pivot and one with elements greater than the pivot.

• Insertion sort is best for small arrays, while quicksort is best for large arrays.

• Both algorithms have an average time complexity of O(n log n)...read more

Operating on images in parallel involves dividing the image into smaller parts and processing them simultaneously.

• Divide the image into smaller parts using techniques like tiling or splitting

• Use parallel processing techniques like multi-threading or GPU acceleration

• Combine the processed parts to form the final image

• Examples: image segmentation, object detection, image enhancement

Hardware engines support parallelism through multiple cores and threads.

• Hardware engines can have multiple cores and threads to execute tasks simultaneously.

• Parallelism can improve performance and efficiency in hardware-based tasks.

• Examples include GPUs, FPGAs, and ASICs that have parallel processing capabilities.

• Hardware parallelism can also be achieved through distributed computing and clustering.

• Programming languages and frameworks like OpenCL and CUDA can be used to lever...read more

Memory protection is a feature of an operating system that prevents unauthorized access to memory locations.

• Memory protection is achieved through the use of memory management units (MMUs) and virtual memory.

• MMUs map virtual addresses to physical addresses and enforce access permissions.

• Virtual memory allows the OS to allocate memory to processes in a way that isolates them from each other.

• Examples of memory protection mechanisms include segmentation, paging, and access contro...read more

Modern OSes support parallelism through multi-core processors and threading.

• Modern OSes like Windows, macOS, and Linux support parallelism through multi-core processors and threading.

• Parallelism can be achieved through processes or threads.

• Parallelism can improve performance and efficiency of software.

• Examples of parallel programming frameworks include OpenMP and MPI.

Diamond hierarchy problem is a problem in object-oriented programming where a class inherits from multiple classes in a diamond-shaped hierarchy.

• Occurs when a class inherits from two classes that share a common base class

• Can lead to ambiguity in method calls and data members

• Solved using virtual inheritance or by using interfaces

Tower of Hanoi is a mathematical puzzle that involves moving a stack of disks from one peg to another.

• The puzzle consists of three pegs and a number of disks of different sizes.

• The objective is to move the entire stack to another peg, obeying the following simple rules:

• - Only one disk can be moved at a time.

• - Each move consists of taking the upper disk from one of the stacks and placing it on top of another stack or on an empty peg.

• - No disk may be placed on top of a smaller ...read more

Find the number of unique paths in a grid from top left to bottom right

• Use dynamic programming to store the number of paths to each cell

• At each cell, the number of paths is the sum of paths from the cell above and the cell to the left

• Example: For a 3x3 grid, there are 6 unique paths