80+ Interview Questions and Answers

Hash table. No, it is not possible to create a data structure with all operations in O(1) time.

• Hash table uses a hash function to map keys to indices in an array.

• Insertion and deletion can be done in O(1) time on average.

• Search retrieval can also be done in O(1) time on average.

• However, worst-case scenarios can result in O(n) time complexity.

• It is not possible to create a data structure with all operations in O(1) time.

Optimized approach to find third largest element from array using half traversal.

• Sort the array in descending order and return the element at index 2.

• Use a max heap to keep track of the top 3 elements while traversing the array.

• Use two variables to keep track of the second and third largest elements while traversing the array.

• Divide the array into two halves and find the maximum and second maximum in each half, then compare them to find the third largest element.

Indexes are used to improve query performance. Multiple clustered and non-clustered indexes can be created on a table.

• Indexes are used to quickly locate data without scanning the entire table.

• Clustered index determines the physical order of data in a table.

• Non-clustered index is a separate structure that contains a copy of the indexed columns and a pointer to the actual data.

• A table can have only one clustered index, but multiple non-clustered indexes.

• Indexes should be create...read more

ACID properties ensure database transactions are reliable. Two transactions can occur simultaneously using locking and isolation.

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

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

• 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.

• Dur...read more

Answering how to print first character of words in a string using one stack and an array.

• For using one stack, push each character onto the stack and pop when a space is encountered. Print the popped character.

• For using an array, split the string into words and print the first character of each word.

• In both cases, handle edge cases like empty string and string with only one word.

Given an array and a number, find if the number can be generated using sum of array members and output those numbers.

• Iterate through the array and check if the number can be generated using the sum of array members

• Use a hash table to store the difference between the number and each array element

• If the difference is found in the hash table, output the corresponding array elements

• If no such combination is found, output 'Not possible'

Time complexity of data structure operations

• Arrays: O(1) for access, O(n) for search/insert/delete

• Linked Lists: O(n) for access/search, O(1) for insert/delete

• Stacks/Queues: O(1) for access/insert/delete

• Hash Tables: O(1) for access/insert/delete (average case)

• Trees: O(log n) for access/search/insert/delete (balanced)

• Heaps: O(log n) for access/insert/delete

• Graphs: Varies depending on algorithm used

Span and div tags are both HTML elements used for grouping content, but they have different purposes.

• Span is an inline element used for grouping text or other inline elements.

• Div is a block-level element used for grouping larger sections of content.

• Span is often used for styling individual words or phrases within a larger block of text.

• Div is often used for creating layout structures and separating content into distinct sections.

• Span elements do not create a new line, while d...read more

Generate all permutations of a given string using recursion and backtracking.

• Use recursion to generate all possible permutations of the string.

• Use backtracking to backtrack and explore all possible combinations.

• Store each permutation in an array of strings.

Reducing page loading time can be achieved through various techniques.

• Optimizing images and videos

• Minimizing HTTP requests

• Using a content delivery network (CDN)

• Enabling browser caching

• Minimizing JavaScript and CSS files

• Using lazy loading for images and videos

• Reducing server response time

• Using gzip compression

• Minimizing redirects

• Using a faster web hosting service

Reversing k nodes in a linked list

• Iterate through the linked list in groups of k nodes

• Reverse each group of k nodes

• Update the pointers accordingly to maintain the reversed order

Joins in SQL are used to combine rows from two or more tables based on a related column between them.

• Joins are used to retrieve data from multiple tables based on a related column

• Common 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

Program to find nth prime number and optimize the code

• Use Sieve of Eratosthenes algorithm to generate prime numbers

• Implement binary search to find nth prime number

• Use memoization to optimize the code

• Avoid unnecessary calculations by checking if a number is prime before checking its factors

Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.

• Normalization is used to eliminate data redundancy by breaking up tables into smaller, related tables.

• There are different normal forms such as 1NF, 2NF, 3NF, BCNF, and 4NF, each with specific rules to follow.

• Normalization helps in reducing data anomalies and ensures data integrity.

• Example: Breaking up a customer table into separate tables for customer details and orde...read more

Use ALTER TABLE to add a new column and then use MAX function to find the highest salary.

• Use ALTER TABLE statement to add a new column to the table.

• Use MAX function in SQL to find the maximum salary of employees.

Cubes are multidimensional data structures used for analysis and reporting. They differ from databases in their structure and purpose.

• Cubes store data in a multidimensional format, allowing for efficient analysis and reporting.

• They are designed to handle large volumes of data and provide fast query performance.

• Cubes use dimensions, measures, and hierarchies to organize and analyze data.

• Unlike databases, cubes are optimized for analytical processing rather than transactional p...read more

Windows and Android OS have evolved with new features and improvements compared to past versions.

• Windows 10 introduced a new Start menu and Cortana virtual assistant.

• Android 11 focused on improved privacy controls and messaging features.

• Both OS have enhanced security measures compared to their past versions.

Count the occurrence of each element in an array of strings

• Iterate through the array and use a hashmap to store the count of each element

• If element already exists in the hashmap, increment its count by 1

• Return the hashmap with element counts

Indexes in SQL are used to improve the performance of queries by allowing the database to quickly retrieve data.

• Indexes are created on columns in a table to speed up data retrieval.

• They work similar to an index in a book, allowing the database to quickly find the relevant data.

• Primary keys automatically have an index created on them.

• Indexes can be unique, meaning that each value in the indexed column must be unique.

• Examples: CREATE INDEX idx_name ON table_name(column_name);

A SQL query to move a table from one schema to another.

• Use the ALTER TABLE statement to rename the table and move it to the new schema.

• Specify the new schema name in the ALTER TABLE statement.

• Ensure that the user executing the query has the necessary privileges to perform the operation.

Program to find length of string using custom function

• Create a custom function that takes an array of strings as input

• Iterate through each string in the array and calculate its length

• Return the lengths of all strings in an array

Reverse the array of strings

• Create a new array and iterate through the original array in reverse order, adding each element to the new array

• Use built-in array methods like reverse() or spread operator for a more concise solution

• Ensure to handle edge cases like empty array or array with only one element

Sort a vector based on another vector

• Use std::sort with a custom comparator function

• The comparator function should compare the indices of the elements in the second vector

• The first vector should be sorted based on the order of the indices in the second vector

A stored procedure is a precompiled set of SQL statements that can be executed on a database server.

• Stored procedures are used to encapsulate and execute complex database operations.

• They can be used to improve performance by reducing network traffic.

• Stored procedures can be parameterized and reused across multiple applications.

• They provide a level of security by allowing access to the database only through the procedure.

• Examples: Creating a stored procedure to insert data int...read more

State management in React involves managing and updating the state of components efficiently.

• Use React's built-in state management with setState() method

• Utilize React Context API for managing global state

• Implement Redux for complex state management in larger applications

Level Order Traversal for Binary Tree is a method to visit all nodes level by level starting from the root.

• Use a queue data structure to keep track of nodes at each level

• Start by pushing the root node into the queue

• While the queue is not empty, dequeue a node, visit it, and enqueue its children

DevOps components include culture, automation, measurement, and sharing.

• Culture: Encouraging collaboration and communication between development and operations teams.

• Automation: Implementing tools for continuous integration, continuous delivery, and infrastructure as code.

• Measurement: Monitoring and analyzing performance metrics to improve processes and identify areas for optimization.

• Sharing: Facilitating knowledge sharing and feedback loops to foster continuous improvement.

A project manager is responsible for planning, executing, and closing projects within a specific timeframe and budget.

• Developing project plans and timelines

• Assigning tasks to team members

• Monitoring progress and adjusting plans as needed

• Communicating with stakeholders

• Ensuring project goals are met within constraints

Replace alternative characters in a string with a specified character

• Iterate through the string and replace characters at odd indices with the specified character

• Use a loop to go through each character and check if its index is odd or even before replacing

• Example: Input string 'hello' and replacement character '*', output 'h*l*'

Left join includes all records from the left table and matching records from the right table, while right join includes all records from the right table and matching records from the left table.

• Left join keeps all records from the left table, even if there are no matches in the right table.

• Right join keeps all records from the right table, even if there are no matches in the left table.

• Example: If we have a table of employees and a table of departments, a left join will inclu...read more

SSMS is a management tool for SQL Server, SSIS is an ETL tool, and SSAS is a BI tool for analyzing data.

• SSMS (SQL Server Management Studio) is a graphical management tool for SQL Server.

• SSIS (SQL Server Integration Services) is an ETL (Extract, Transform, Load) tool used for data integration and workflow applications.

• SSAS (SQL Server Analysis Services) is a BI (Business Intelligence) tool used for analyzing and reporting data.

• SSMS is used for managing databases, creating and ...read more

Calculate the sum of digits of a given number.

• Iterate through each digit of the number and add them together.

• Use modulo operator to extract each digit.

• Repeat until all digits are processed.

• Example: For number 123, sum of digits = 1 + 2 + 3 = 6.

ATM (Automated Teller Machine) is an electronic banking outlet that allows customers to complete basic transactions without the aid of a branch representative.

• ATMs allow customers to withdraw cash, deposit checks, transfer money between accounts, and check account balances.

• ATMs communicate with the bank's computer system to verify account information and process transactions.

• ATMs use a magnetic stripe or chip on the customer's debit or credit card to identify the account and ...read more

Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. Keys are used to uniquely identify records in a table.

• Normalization involves breaking down data into smaller, more manageable parts to reduce redundancy.

• Keys are used to uniquely identify records in a table. Examples include primary keys, foreign keys, and candidate keys.

• Normalization helps in maintaining data integrity and reducing anomalies such as insertion, updat...read more

Sort an array of strings containing '0', '1', and '2'.

• Use counting sort algorithm to count the occurrences of '0', '1', and '2'.

• Create a new array with the sorted counts of '0', '1', and '2'.

• Join the sorted array back into a single array of strings.