10+ Accion Labs Interview Questions and Answers

Multitasking in Java can be achieved using threads.

• Create multiple threads to execute tasks concurrently.

• Use the Thread class or the Runnable interface to define the tasks.

• Use synchronization mechanisms like locks or semaphores to coordinate access to shared resources.

• Java provides built-in support for multitasking with the Thread class and the Executor framework.

• Example: creating two threads to perform different tasks simultaneously.

ACID properties are a set of properties that guarantee reliability and consistency in database transactions.

• ACID stands for Atomicity, Consistency, Isolation, and Durability.

• Atomicity ensures that a transaction is treated as a single unit of work, either all of its operations are executed or none.

• Consistency ensures that a transaction brings the database from one valid state to another.

• Isolation ensures that concurrent transactions do not interfere with each other.

• Durability ...read more

A transaction is a logical unit of work that consists of multiple database operations that must be executed as a single, indivisible unit.

• A transaction ensures data consistency and integrity.

• It follows the ACID properties: Atomicity, Consistency, Isolation, and Durability.

• Transactions are used to maintain data integrity in databases.

• Examples of transactions include transferring funds between bank accounts or updating inventory levels.

Design a schema for a restaurant app like Zomato.

• Create tables for restaurants, users, reviews, and orders

• Include columns for restaurant details like name, address, cuisine type

• Include columns for user details like name, email, and password

• Link reviews to restaurants and users

• Link orders to restaurants and users

• Consider additional tables for menu items, categories, and ratings

Find first missing positive integer from an array of non-negative integers.

• Create a hash set to store all positive integers in the array

• Loop through the array and add all positive integers to the hash set

• Loop through positive integers starting from 1 and return the first missing integer not in the hash set

A semaphore is a synchronization object that controls access to a shared resource through the use of a counter.

• Semaphores are used to manage concurrent access to shared resources in multi-threaded or multi-process environments.

• They can be used to limit the number of threads or processes that can access a resource simultaneously.

• Semaphores can have two types: counting semaphores and binary semaphores.

• Counting semaphores allow multiple threads/processes to access a resource at ...read more

SQL databases are relational databases that use structured query language, while NoSQL databases are non-relational databases that use various data models.

• SQL databases are based on a fixed schema, while NoSQL databases are schema-less.

• SQL databases are better suited for complex queries and structured data, while NoSQL databases are better for unstructured and semi-structured data.

• SQL databases ensure ACID (Atomicity, Consistency, Isolation, Durability) properties, while NoSQ...read more

Group list of strings into distinct anagrams.

• Create a hash table with sorted string as key and list of anagrams as value.

• Iterate through the list of strings and add each string to its corresponding anagram list in the hash table.

• Return the values of the hash table as a list of lists.

Find the lowest common ancestor of a binary tree.

• Traverse the tree recursively from the root node.

• If the current node is null or matches either of the given nodes, return the current node.

• Recursively search for the nodes in the left and right subtrees.

• If both nodes are found in different subtrees, return the current node.

• If both nodes are found in the same subtree, continue the search in that subtree.

The minimum weight to reach the bottom right corner in a matrix starting from the top left by moving only down and right.

• Use dynamic programming to calculate the minimum weight at each cell by considering the weights of the cells above and to the left.

• At each cell, the minimum weight to reach that cell is the minimum of the weight of the cell itself plus the minimum weight of the cells above and to the left.

• Example: For a matrix [[1, 3, 1], [1, 5, 1], [4, 2, 1]], the minimum ...read more

Multitasking in Java can be achieved through multithreading.

• Create a new thread using the Thread class or Runnable interface

• Use the start() method to start the thread

• Synchronize shared resources to avoid race conditions

• Use wait() and notify() methods for inter-thread communication

• Example: creating a thread to perform a long-running task while the main thread continues executing other tasks

Design a schema for a restaurant app like Zomato.

• Create tables for restaurants, menus, reviews, and users.

• Include columns for restaurant name, location, cuisine, and ratings.

• Add columns for menu items, prices, and descriptions.

• Include user information such as name, email, and password.

• Create relationships between tables using foreign keys.

• Implement search and filter functionality for restaurants and menus.

• Allow users to leave reviews and ratings for restaurants.

• Include featur...read more

SQL is a relational database while NoSQL is a non-relational database.

• SQL databases use structured query language while NoSQL databases use unstructured query language.

• SQL databases are vertically scalable while NoSQL databases are horizontally scalable.

• SQL databases are good for complex queries while NoSQL databases are good for large amounts of unstructured data.

• Examples of SQL databases include MySQL, Oracle, and PostgreSQL while examples of NoSQL databases include MongoDB...read more

Design a parking lot

• Consider the size and capacity of the parking lot

• Decide on the layout and organization of parking spaces

• Implement a system to manage parking availability and reservations

• Include features like ticketing, payment, and security

• Consider scalability and future expansion

Semaphores are a synchronization tool used to control access to a shared resource.

• Semaphores can be used to prevent race conditions in multi-threaded programs.

• They can be used to limit the number of concurrent accesses to a resource.

• Semaphores can be binary (0 or 1) or counting (0 to n).

• Examples of semaphore functions include wait(), signal(), and init().

A transaction is a unit of work that is performed on a database.

• A transaction is a sequence of database operations that are treated as a single unit of work.

• It ensures that all the operations are completed successfully or none of them are performed.

• Transactions are used to maintain data consistency and integrity in a database.

• Examples of transactions include transferring money between bank accounts or updating inventory levels in a retail system.