10+ Perfios Software Solutions Interview Questions and Answers

Implementing a palindrome check in Java without using the reverse() function.

• Create a function that takes a string as input.

• Use two pointers, one starting from the beginning of the string and the other from the end.

• Compare characters at the two pointers and move them towards each other until they meet or cross.

• If all characters match, the string is a palindrome.

• Example: 'racecar' is a palindrome.

• Example: 'hello' is not a palindrome.

Rotate an array of strings by n positions

• Create a new array and copy elements from original array starting from index n to the end, then copy elements from index 0 to n-1

• Alternatively, you can use array slicing to achieve the rotation

• Example: Original array ['a', 'b', 'c', 'd', 'e'], rotate by 2 positions would result in ['c', 'd', 'e', 'a', 'b']

The algorithm to reverse a singly linked list involves iterating through the list and changing the pointers to reverse the direction of the links.

• Start with three pointers: current, previous, and next.

• Iterate through the list, updating the next pointer to point to the previous node.

• Move the previous pointer to the current node and the current pointer to the next node.

• Continue until the end of the list is reached, then update the head of the list to the last node visited.

Use counting method to sort array of strings with 0's and 1's.

• Create a count array to store the frequency of 0's and 1's.

• Update the original array based on the count array.

• Example: Input array - ['0', '1', '0', '1', '1'], Output array - ['0', '0', '1', '1', '1']

HTTPS provides secure communication over the internet using encryption, while HTTP does not.

• HTTPS uses SSL/TLS encryption to secure data transmission, while HTTP does not.

• HTTPS URLs begin with 'https://' and use port 443, while HTTP URLs begin with 'http://' and use port 80.

• HTTPS ensures data integrity and authentication, while HTTP does not provide these security measures.

SQL query to retrieve data from employee table

• Use SELECT statement to retrieve data

• Specify the columns you want to retrieve

• Use FROM clause to specify the table name

• Add any conditions using WHERE clause if needed

Use ORDER BY and LIMIT to get last entry in SQL query

• Use ORDER BY column_name DESC to sort in descending order

• Use LIMIT 1 to get only the last entry

Alarm clocks in phones work by triggering a pre-set notification at a specific time to alert the user.

• Alarm clock app is programmed to trigger a notification at a specific time set by the user

• The phone's system clock is used to track the current time and compare it to the set alarm time

• When the alarm time matches the current time, the phone plays the selected alarm sound or vibration

• Users can customize alarm settings such as sound, snooze duration, and repeat options

Designed DB schema and API for internship project

• Created normalized database schema to store user information, orders, and products

• Implemented RESTful API endpoints for CRUD operations on user data

• Used authentication and authorization mechanisms to secure API endpoints

• Optimized queries for efficient data retrieval and processing

Hash map is a data structure that stores key-value pairs and uses a hash function to map keys to their corresponding values.

• Hash map uses a hash function to determine the index of the key-value pair in the underlying array.

• Collisions can occur when two keys hash to the same index, which can be resolved using techniques like chaining or open addressing.

• Hash maps offer constant time complexity O(1) for insertion, deletion, and lookup operations on average.

• Example: HashMap<Strin...read more

Repeating DNA sequences can lead to genetic disorders.

• Repeating DNA sequences can cause genetic disorders such as Huntington's disease.

• These repeats can expand in size over generations, leading to more severe symptoms.

• PCR and DNA sequencing techniques can be used to detect and analyze these repeats.

B/S stands for Balance Sheet, which represents the financial position of a company at a specific point in time. P&L stands for Profit and Loss statement, which shows the financial performance of a company over a specific period.

• Balance Sheet (B/S) provides a snapshot of a company's assets, liabilities, and shareholders' equity at a given date.

• It helps in assessing the financial health, liquidity, and solvency of a company.

• B/S includes items such as cash, accounts receivable, ...read more

Data Structures and Algorithms are used in real life applications such as social media algorithms, GPS navigation, and search engines.

• Social media algorithms use DSA to personalize user feeds based on their interests and interactions.

• GPS navigation systems use Dijkstra's algorithm to find the shortest route between two locations.

• Search engines like Google use algorithms like PageRank to rank web pages based on relevance and importance.

React is better than plain JavaScript for building complex user interfaces due to its component-based architecture and virtual DOM.

• React allows for easier management of state and props through its component-based architecture.

• Virtual DOM in React helps improve performance by only updating the necessary parts of the actual DOM.

• React's declarative approach simplifies the process of building and maintaining complex UIs.

• React ecosystem provides a wide range of tools and libraries...read more

Data structures are ways of organizing and storing data in a computer so that it can be accessed and used efficiently.

• Data structures are used to manage and manipulate data in computer programs.

• They can be implemented using arrays, linked lists, trees, graphs, and other techniques.

• Examples of data structures include stacks, queues, hash tables, and binary search trees.

• Choosing the right data structure for a particular problem can greatly improve the efficiency of a program.

APIs (Application Programming Interfaces) are sets of rules and protocols that allow different software applications to communicate with each other.

• APIs define the methods and data formats that applications can use to request and exchange information.

• They allow developers to access the functionality of a system or service without needing to understand its internal workings.

• Examples of APIs include Google Maps API for integrating maps into applications, Twitter API for accessi...read more

B/S (Balance Sheet) shows a company's financial position at a specific point in time, while P&L (Profit and Loss) shows its financial performance over a period of time.

• B/S reports assets, liabilities, and equity at a specific date.

• P&L reports revenues, expenses, and net income over a period.

• B/S helps assess solvency and liquidity.

• P&L helps evaluate profitability and operational efficiency.

• Example: B/S shows cash, inventory, and debt as of December 31st, while P&L shows revenu...read more