Grey Orange Hardware Engineer Interview Questions and Answers

An immutable class is a class whose instances cannot be modified after creation.

• Make all fields private and final

• Don't provide any setter methods

• Ensure that any mutable objects passed to the constructor are defensively copied

• Make the class final so that it cannot be subclassed

Singleton pattern ensures only one instance of a class is created and provides a global point of access to it.

• Create a private constructor to prevent direct instantiation of the class.

• Create a private static instance of the class.

• Create a public static method to access the instance, and create the instance if it doesn't exist.

• Ensure thread safety by using synchronized keyword or double-checked locking.

Vector is synchronized and ArrayList is not. Vector is thread-safe and ArrayList is not.

• Vector is a legacy class and ArrayList is a part of the Java Collection Framework.

• Vector is synchronized which means only one thread can access it at a time, while ArrayList is not.

• Vector is thread-safe which means it can be used in a multi-threaded environment, while ArrayList is not.

• Vector is slower than ArrayList because of synch...read more

Create Linked List without using internal library and provide add, delete, find functionality.

• Create a Node class with data and next pointer

• Create a LinkedList class with head pointer and methods to add, delete, and find nodes

• Use a loop to traverse the list and perform operations

• Handle edge cases such as adding to an empty list or deleting the head node

The current system follows a microservices architecture.

• The system is divided into multiple independent services.

• Each service has its own database and communicates with other services through APIs.

• The architecture allows for scalability and flexibility.

• Examples of microservices used in the system include user authentication, payment processing, and inventory management.

Find the total no of islands in a 2D matrix.

• Use DFS or BFS to traverse the matrix.

• Mark visited cells to avoid repetition.

• Count the number of islands found.

Loop detection in a linked list.

• Use two pointers, one moving at twice the speed of the other.

• If there is a loop, the faster pointer will eventually catch up to the slower one.

• If there is no loop, the faster pointer will reach the end of the list.

Regex for email validation

• Start with a string of characters followed by @ symbol

• Followed by a string of characters and a period

• End with a string of characters with a length of 2-6 characters

• Allow for optional subdomains separated by periods

• Disallow special characters except for . and _ in username

Print prime numbers in a given range and optimize the solution.

• Use Sieve of Eratosthenes algorithm to generate prime numbers efficiently

• Start with a boolean array of size n+1, mark all as true

• Loop through the array and mark all multiples of each prime as false

• Print all the indexes that are still marked as true

Find angle between hour and minute hand in a clock given the time.

• Calculate the angle made by the hour hand with respect to 12 o'clock position

• Calculate the angle made by the minute hand with respect to 12 o'clock position

• Find the difference between the two angles and take the absolute value

• If the angle is greater than 180 degrees, subtract it from 360 degrees to get the smaller angle

To un-hash a string, use a reverse algorithm to convert the hash back to the original string.

• Create a reverse algorithm that takes the hash as input and outputs the original string

• Use the same logic as the hash function but in reverse order

• If the hash function used a specific algorithm, use the inverse of that algorithm to un-hash the string

I want you to provide me with challenging software development projects that will help me grow as a developer.

• Challenging projects that will push my skills to the limit

• Opportunities to learn new technologies and programming languages

• Collaborative work environment with experienced developers

• Clear communication and feedback on my work

• Opportunities for career growth and advancement

Find Nth largest element in the BST

• Traverse the BST in reverse inorder and keep track of count

• If count equals N, return the current node's value

• If count exceeds N, stop traversing and return null

• If count is less than N, continue traversing

Find node in BST with value equal to or greater than input value.

• Start at root node

• If input value is less than current node value, move to left child

• If input value is greater than or equal to current node value, move to right child

• Repeat until node with desired value is found or null is reached

Program to check if a binary tree is balanced

• Calculate height of left and right subtrees recursively

• Check if the difference in height is not more than 1

• Repeat for all nodes in the tree

• Time complexity: O(nlogn) or O(n)

• Space complexity: O(h) where h is the height of the tree

Find max size of a sub-string with no duplicate characters in a given string.

• Use a sliding window approach with two pointers.

• Maintain a hash set to keep track of unique characters.

• Update the maximum length of the substring as you iterate through the string.

A hash table is a data structure that stores key-value pairs and uses a hash function to map keys to buckets.

• Hash function takes a key and returns an index to a bucket

• Collisions occur when multiple keys map to the same bucket

• Collision resolution techniques include chaining and open addressing

• Example: Dictionary in Python uses hash tables to store key-value pairs

WAP to find a continuous subset divisible by 7 from an array of numbers. Calculate algorithm complexity.

• Iterate through the array and calculate the prefix sum modulo 7 at each index.

• Store the prefix sum modulo 7 in a hash table with the index as the value.

• If a prefix sum modulo 7 is already in the hash table, the subarray between the two indices has a sum divisible by 7.

• Time complexity is O(n) and space complexity is O

Given a 2D array of integers, set rows and columns to 1 if they contain 1.

• Iterate through the array to find the index of 1

• Use two arrays to keep track of rows and columns with 1

• Iterate through the rows and columns arrays to set values to 1

Code to find sum of two numbers stored as linked list.

• Traverse both lists simultaneously and add corresponding nodes

• Keep track of carry and add it to next sum

• Create a new node for each sum and move to next node

Code to print elements on path from root to leaf node with max sum

• Traverse the tree and keep track of the maximum sum path

• Use recursion to traverse the tree

• Print the path when a leaf node with maximum sum is reached

Retrieving min element from a max heap has a time complexity of O(log n).

• The min element is always the leftmost leaf node in the last level of the heap.

• To retrieve it, swap it with the last element in the heap and remove it.

• Then, bubble down the new root to maintain the max heap property.

• Examples: retrieving the smallest number in a priority queue implemented as a max heap.

• Examples: retrieving the smallest element in a

The fastest method to sort an almost sorted array is shell sort.

• Shell sort has a time complexity of O(n log n) which is faster than bubble sort and insertion sort.

• Quick sort and merge sort have a time complexity of O(n log n) but they are not optimized for almost sorted arrays.

• Shell sort works by comparing elements that are far apart first and then gradually reducing the gap between them.

• Example: If the array is [1, 3,...read more

A zombie process is a process that has completed execution but still has an entry in the process table.

• Zombie processes occur when a parent process does not properly wait for its child process to terminate.

• The zombie process remains in the process table until the parent process reads its exit status.

• Zombie processes do not consume system resources but can accumulate if not properly handled.

• They can be identified using ...read more

Hash tables have complexities related to collisions, resizing, and choosing a good hash function.

• Collisions occur when two keys map to the same index, requiring a collision resolution strategy.

• Resizing can be expensive as all elements need to be rehashed and moved to new locations.

• Choosing a good hash function is important to minimize collisions and ensure even distribution of keys.

• Examples of collision resolution stra...read more

Algorithm to find any three numbers in an array that sum to zero.

• Sort the array in ascending order.

• Loop through the array and fix the first number.

• Use two pointers to find the other two numbers that sum to the negative of the fixed number.

• If found, return the three numbers.

• If not found, move to the next number and repeat the process.

• Time complexity: O(n^2)

Returning kth smallest element in a BST with time complexity logn.

• Perform in-order traversal and keep track of count until kth element is reached

• If kth element is found, return it

• If kth element is not found, continue traversal

• If traversal is complete and kth element is not found, return null

• Time complexity is logn as we only traverse the height of the tree