100+ YDTS India Interview Questions and Answers

Client-server code with optimal thread handling for multiple requests

• Use a thread pool to handle multiple requests efficiently

• Optimal number of threads depends on CPU cores and available memory

• Increasing threads beyond optimal number can lead to resource contention and performance degradation

Using two hour glasses, one emptied in 4 minutes and another in 7 minutes, calculate 9 minutes.

• Start both hour glasses simultaneously

• When the 4-minute hour glass is empty, flip it again

• When the 7-minute hour glass is empty, 4 minutes have passed

• Flip the 7-minute hour glass again and wait for it to empty

• When it's empty, 9 minutes have passed

To find 2 defective vending machines out of n machines in O(1) time, label each machine with a unique number and use XOR operation.

• Label each machine with a unique number from 1 to n

• Calculate the XOR of all the numbers from 1 to n and the XOR of all the numbers of the working machines

• The result of XORing these two values will give the XOR of the two defective machines

• Find the rightmost set bit in the XOR result, divide the machines into two groups based on that bit, and XOR t...read more

Given a string with characters separated by spaces, return each character as a separate string without using extra space.

• Split the string by spaces to get an array of characters

• Return the array of characters as individual strings

Implementing qsort() or custom sort() function in C/C++ to sort any type of data based on user-defined criteria.

• Use qsort() function in C or sort() function in C++ to sort the data.

• For custom sorting, define a comparison function that takes two elements and returns a negative, zero, or positive value based on their order.

• The comparison function should be passed as a parameter to qsort() or sort() function.

• Ensure the comparison function handles different data types and user-de...read more

To make the most optimized triangular mesh, use a Delaunay triangulation algorithm.

• Use a Delaunay triangulation algorithm to connect the points with triangles.

• Delaunay triangulation ensures that no point is inside the circumcircle of any triangle.

• This algorithm creates triangles with the minimum angle possible, resulting in an optimized mesh.

• Popular algorithms for Delaunay triangulation include Bowyer-Watson and incremental algorithms.

The running time for insertion, deletion, and searching in a sorted array is O(log n), while in an unsorted array it is O(n).

• In a sorted array, insertion, deletion, and searching can be done using binary search, which has a time complexity of O(log n).

• In an unsorted array, insertion and deletion require shifting elements, resulting in a time complexity of O(n). Searching also requires checking each element, resulting in a time complexity of O(n).

C/C++ memory allocation differences between new/malloc, free/delete, and details on how memory allocation takes place.

• C/C++ use new/delete for objects and malloc/free for raw memory allocation

• new calls constructor, malloc does not

• delete calls destructor, free does not

• new throws exception on failure, malloc returns NULL

• Memory allocation involves finding a contiguous block of memory and marking it as allocated

Use quicksort algorithm to match nuts and bolts in minimum iterations.

• Use quicksort algorithm to sort both nuts and bolts arrays based on diameter.

• Compare each nut with each bolt to find matching pairs.

• Time complexity is O(nlogn) using quicksort.

Multithreading allows multiple threads to run concurrently. Global and static variables are stored in a shared memory space and accessed by all threads.

• Multithreading enables concurrent execution of multiple threads.

• Global and static variables are stored in a shared memory space accessible by all threads.

• Threads can read and modify the values of global and static variables.

• Synchronization mechanisms like locks or semaphores are used to prevent data races and ensure thread saf...read more

To generate 0-7 with equal probability, use F() twice to generate a binary number and convert it to decimal.

• Call F() twice to generate two binary digits

• Combine the two binary digits to form a binary number

• Convert the binary number to decimal to get a number between 0-3

• Multiply the decimal number by 2 to get a number between 0-6

• Add 1 to the result to get a number between 1-7

Check if second string is a substring of the first string with wildcard characters.

• Use a sliding window approach to compare characters of both strings.

• Handle wildcard characters '*' and '?' appropriately.

• Consider all possible combinations of wildcard characters in the second string.

Reverse a given linked list to create a new linked list.

• Traverse the original linked list and store each node in a stack

• Pop elements from the stack to create a new linked list in reverse order

Local variables are stored on the stack, dynamic allocated variables are stored on the heap, and global variables are stored in the data segment.

• Local variables are stored on the stack and are only accessible within the scope of the function where they are declared.

• Dynamic allocated variables are stored on the heap and can be accessed globally by different parts of the program.

• Global variables are stored in the data segment and can be accessed from any part of the program.

HashMap can be used to store patient information in a hospital. Array can be used to store a list of medications.

• HashMap: Store patient ID as key and patient information as value

• Array: Store list of medications prescribed to a patient

Sort array with even indices smaller than odd and odd indices greater than even.

• Loop through array and swap elements if necessary

• Use a temporary variable to swap elements

• Compare current element with its even/odd indexed neighbour

Operator overloading can be used to multiply two objects by defining a custom operator function.

• Define a member function for the class that overloads the * operator

• Inside the function, perform the multiplication operation on the object's data members

• Return the result of the multiplication operation

Create AVL tree and BST from given numbers with rotations.

• Start by creating a binary search tree (BST) with the given numbers.

• Then, balance the BST by performing rotations to create an AVL tree.

• AVL tree rotations include left-left, right-right, left-right, and right-left rotations.

• Ensure that the AVL tree maintains the balance factor of each node.

• The final AVL tree should have the numbers 5, 7, 10, 20, and 30 in the correct order.

This C program selects a contiguous subarray of size m from an array with the sum closest to zero.

• Iterate through the array and calculate the sum of each subarray of size m

• Keep track of the subarray with the closest sum to zero

• Return the subarray with the closest sum to zero

The longest common substring between two strings can be found using dynamic programming or trie.

• Dynamic programming approach involves creating a matrix to store the lengths of common substrings at each position.

• Trie approach involves inserting all substrings of one string into a trie and then finding the longest common prefix with the other string.

• Examples: For strings 'ABCD' and 'BCDE', the longest common substring is 'BC'. For strings 'ABC' and 'DEF', there is no common sub...read more

Program to search an element in a sorted 2D array

• Start from the top-right corner of the array

• Compare the target element with the current element

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

• Repeat until the target is found or the boundaries are crossed

The question asks about the output of expanding a macro in C, emphasizing the need for careful expansion to avoid incorrect results.

• Macro expansion in C involves replacing the macro with its corresponding code before compilation.

• If the expansion is not done carefully, it can lead to unexpected or incorrect results.

• Careful expansion includes considering operator precedence, parentheses, and proper substitution.

• Example: Given a macro #define SQUARE(x) x * x, expanding SQUARE(2+...read more

A program to convert a binary tree to binary search tree.

• Perform an inorder traversal of the binary tree to get the sorted elements.

• Create a new binary search tree and insert the sorted elements in the correct order.

• The resulting binary search tree will have the same elements as the original binary tree, but in sorted order.

A function to find the second largest element in an array.

• Sort the array in descending order

• Return the element at index 1

It depends on the specific use case and requirements.

• Consider the type of data being stored and the operations that need to be performed on it.

• Common data structures include arrays, linked lists, stacks, queues, trees, and graphs.

• For example, if the data needs to be accessed randomly and quickly, an array may be the best choice.

• If the data needs to be sorted or searched frequently, a tree or hash table may be more appropriate.

• Ultimately, the choice of data structure will depe...read more

Converting a number from base 11 to base 7 involves dividing the number by 7 and keeping track of remainders.

• Divide the number in base 11 by 7 and keep track of remainders

• Repeat the process with the quotient until it becomes 0

• The remainders obtained in reverse order will give the number in base 7

Intersection of two lines in a plane can be determined by solving the equations of the lines simultaneously.

• To find the point of intersection, set the equations of the two lines equal to each other and solve for the variables.

• If the lines are in slope-intercept form (y = mx + b), set the two equations equal to each other and solve for x and y.

• If the lines are in standard form (Ax + By = C), solve the system of equations to find the point of intersection.

This function replaces a specified string with another string in a given paragraph.

• Use the replace() method to replace the string.

• Pass the original string, the string to be replaced, and the replacement string as arguments to the replace() method.

• The replace() method returns a new string with the replacements made.

The size of a structure in C depends on the size of its members, including unions and enums.

• The size of a structure is determined by the sum of the sizes of its members.

• Unions share the same memory space, so the size of a union is equal to the size of its largest member.

• Enums are typically represented as integers, so their size depends on the size of an integer in the system.

Quick sort is faster on average but merge sort is more stable and guarantees O(n log n) time complexity.

• Quick sort has an average time complexity of O(n log n) and is in-place, but worst-case time complexity of O(n^2).

• Merge sort has a stable time complexity of O(n log n) but requires extra space for merging.

• Quick sort is not stable, while merge sort is stable.

• Quick sort is often preferred for arrays with a large number of elements, while merge sort is preferred for linked lis...read more

Find the first common ancestor of two nodes in a binary tree.

• Traverse the tree from the root node and check if both nodes are in the left or right subtree of the current node.

• If they are in different subtrees, then the current node is the first common ancestor.

• If they are in the same subtree, continue traversing that subtree until they are in different subtrees.

• If one of the nodes is the ancestor of the other, return the ancestor node.

• If one of the nodes is not in the tree, r...read more

To list all unique filenames in a directory in minimum time.

• Use a hash set to store unique filenames

• Iterate through each file in the directory

• Check if the filename is already in the hash set, if not, add it

• Return the hash set as an array of strings

Virtual memory is a memory management technique that allows the computer to use secondary storage as an extension of RAM.

• Virtual memory is a combination of RAM and disk space.

• It allows the computer to run more programs than it has physical RAM for.

• When a program needs more memory than is available in RAM, the operating system moves some data from RAM to disk, freeing up space for other programs.

• This swapping of data between RAM and disk is known as paging.

• Thrashing occurs whe...read more

The least common ancestor (LCA) is the lowest node that has both given nodes as descendants.

• For a binary search tree (BST), the LCA can be found by comparing the values of the nodes with the given nodes.

• For a binary tree, the LCA can be found by recursively searching for the nodes in the left and right subtrees.

• If one of the given nodes is the ancestor of the other, it is considered as the LCA.

Reversing a singly linked list involves changing the direction of pointers, while reversing a doubly linked list involves swapping the previous and next pointers.

• For singly linked list: iterate through the list and change the direction of pointers to reverse the list.

• For doubly linked list: swap the previous and next pointers of each node to reverse the list.

• Example for singly linked list: 1 -> 2 -> 3 -> 4 -> null, after reversing: 4 -> 3 -> 2 -> 1 -> null

• Example for doubly l...read more

Producer Consumer semaphore code using semwait and semsignal

• Use semaphores to control access to shared buffer between producer and consumer

• Producer signals when it adds an item to the buffer using semsignal

• Consumer waits for signal from producer before consuming item using semwait

Find number of triplets in array whose sum is less than or equal to target.

• Sort the array in ascending order.

• Use three pointers to iterate through the array and find triplets.

• Update pointers based on sum of triplets and target value.

To implement a contiguous 2-d matrix dynamically in C, you can use a single-dimensional array and calculate the index based on row and column.

• Allocate memory for the matrix using malloc or calloc

• Access elements using a formula: index = (row * numColumns) + column

• Free the memory after use to avoid memory leaks

The interviewee was asked to complete code for a 4x4 matrix and run it.

• Ensure the code initializes a 4x4 matrix

• Check for any syntax errors or logical mistakes

• Run the code to verify the output

The question is about the Chief Ministers of some states and the latest Android version.

• The Chief Minister of Maharashtra is Uddhav Thackeray.

• The Chief Minister of Tamil Nadu is M.K. Stalin.

• The latest Android version is Android 12.

Allocate a two-dimensional matrix using the 'new' keyword.

• Use the 'new' keyword to dynamically allocate memory for the matrix.

• Specify the number of rows and columns in the matrix.

• Access elements using the row and column indices.

• Remember to deallocate the memory using 'delete' when done.

Cloning a linked list with random pointers.

• Create a copy of each node and insert it next to the original node.

• Update the random pointers of the copied nodes to point to the corresponding copied nodes.

• Separate the original and copied nodes to get the cloned linked list.

Using ternary operator to find the maximum of three numbers

• Use ternary operator to compare the first two numbers, then compare the result with the third number

• Example: int max = (a > b) ? ((a > c) ? a : c) : ((b > c) ? b : c);

Find the second largest element in a given array of strings.

• Sort the array in descending order.

• Access the element at index 1 to get the second largest element.

• Handle cases where there may be duplicates or less than 2 elements in the array.

Spiral order traversal of a matrix is a way to visit all elements in a matrix in a spiral pattern.

• Start by traversing the outermost layer of the matrix from left to right, top to bottom, right to left, and bottom to top.

• Continue this pattern for each inner layer until all elements are visited.

• Keep track of the boundaries of the matrix to know when to stop.

The lowest common ancestor of a Binary Search Tree (BST) is the node that is the closest common ancestor of two given nodes.

• Traverse the BST starting from the root node

• Compare the values of the two given nodes with the current node's value

• If both nodes are on the same side of the current node, move to that side

• If the nodes are on different sides, the current node is the lowest common ancestor

To find the middle of a linked list in one traversal, use two pointers - one moving at double the speed of the other.

• Use two pointers - slow and fast, with fast moving twice as fast as slow

• When fast reaches the end, slow will be at the middle of the linked list

Evaluation of a prefix expression involves evaluating operators before operands.

• Start from the rightmost element and move towards the left.

• When encountering an operator, apply it to the next two elements in the expression.

• Repeat until the entire expression is evaluated.

• Example: + * 2 3 4 would be evaluated as (2 * 3) + 4 = 10.

Implement a queue using two stacks

• Use two stacks to simulate the behavior of a queue

• One stack for enqueue operation and another for dequeue operation

• When dequeue is called, check if the second stack is empty, if so, transfer elements from the first stack

The Fibonacci sequence is a series of numbers in which each number is the sum of the two preceding ones.

• The Fibonacci sequence starts with 0 and 1.

• Each subsequent number is the sum of the two preceding numbers.

• The formula to calculate the nth term of the Fibonacci sequence is F(n) = F(n-1) + F(n-2).

• For example, the 6th term of the Fibonacci sequence is 8, as 0 + 1 + 1 + 2 + 3 + 5 = 8.

Pointers to functions are used to store the address of functions in C programming.

• Pointers to functions are declared using the function's return type and parameters.

• They can be used to call functions indirectly.

• Example: int (*ptr)(int, int);

• Example: ptr = &add; ptr(10, 20);

Implement a queue using stacks

• Use two stacks to simulate the behavior of a queue

• One stack is used for enqueue operation and the other for dequeue operation

• When enqueueing, push elements into the enqueue stack

• When dequeuing, if the dequeue stack is empty, transfer elements from enqueue stack to dequeue stack

• Return the top element of the dequeue stack for dequeue operation

Code for creating a directory structure in a programming language

• Use mkdir() function in C to create directories

• Use os.makedirs() in Python to create directories recursively

• Use mkdirs() in Java to create directories recursively

Garbage collection algorithms manage memory in programming languages by automatically reclaiming unused memory.

• Garbage collection is used in languages like Java, C#, and Python to automatically free up memory.

• There are different algorithms like mark and sweep, reference counting, and generational collection.

• Mark and sweep algorithm involves marking reachable objects and then sweeping away the unmarked ones.

• Reference counting algorithm counts references to objects and dealloca...read more

The full booting procedure is the sequence of steps that a computer system goes through to start up and become operational.

• Power on the computer

• Perform the Power-On Self-Test (POST)

• Load the Basic Input/Output System (BIOS)

• Initialize hardware components

• Load the operating system

• Initialize software components

• Display the login screen or desktop

Design a maze problem with varying difficulty levels.

• Start by designing a simple maze with one entrance and one exit.

• Increase difficulty by adding dead ends, loops, and multiple paths.

• Include obstacles like walls or traps to make the maze more challenging.

• Consider adding different levels with increasing complexity for players to progress through.

• Provide hints or clues for players to navigate through the maze.

• Allow for customization options such as maze size, shape, and theme....read more

Assembly language output refers to the machine code generated by an assembler from assembly language code.

• Assembly language is a low-level programming language that is closely related to machine code.

• The output of an assembler is typically in the form of machine code instructions that can be directly executed by a computer.

• Assembly language output is specific to the architecture of the target processor.

• Example: MOV AX, 5h - this assembly language instruction would be translat...read more

The Convex Hull problem involves finding the smallest convex polygon that encloses a set of points.

• The Convex Hull is the smallest convex polygon that encloses all given points.

• Common algorithms for solving the Convex Hull problem include Graham's scan and Jarvis march.

• The Convex Hull problem is often used in computer graphics, image processing, and computational geometry.

My 5-year plan involves advancing my career through continuous learning and professional development.

• Continuously seek out new learning opportunities and certifications

• Set specific career goals and milestones to track progress

• Network with industry professionals and mentors for guidance

• Regularly reassess and adjust the plan based on career developments