Stashfin Senior Software Engineer Interview Questions and Answers

Q1. Machine coding round for SQL
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Q1. Minimum number of platforms required for train station
Ans. 
Minimum of two platforms are required for a train station.
• At least two platforms are needed for trains to arrive and depart simultaneously.

• Additional platforms may be required depending on the frequency of trains and passenger traffic.

• Platforms should be long enough to accommodate the longest trains that will use the station.
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Q2. Longest Palindromic substring
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The problem is to find the longest substring that is a palindrome in a given string.
• A palindrome is a string that reads the same backward as forward.

• We can use dynamic programming to solve this problem.

• We can start by considering each character as the center of a palindrome and expand outwards to find the longest palindrome.

• We can also optimize the solution by using Manacher's algorithm which reduces the time complexit
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Q1. Sort the elements of an unsorted array
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Use any sorting algorithm to sort the elements of an unsorted array.
• Choose an appropriate sorting algorithm based on the size of the array and the type of elements.

• Common sorting algorithms include bubble sort, insertion sort, selection sort, merge sort, quick sort, and heap sort.

• Implement the chosen algorithm in the programming language of your choice.

• Test the sorting function with various input arrays to ensure corre
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Q2. Minimum energy required to cross all the hurdles without loosing life. If any point energy becomes 0 game over. Input: [-2,-3,3,1,5]
Ans. 
Find minimum energy required to cross all hurdles without losing life.
• Calculate cumulative sum of energy required to cross each hurdle.

• Find the minimum cumulative sum and add 1 to it.

• If the minimum cumulative sum is negative, return its absolute value + 1.

• This is the minimum energy required to cross all hurdles without losing life.
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DP questions 1D DP and Array question

Q1. Java questions and technical questions from previous experience
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Q1. Behavioural questions and standard HR questions
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Q2. Why looking for job switch
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Seeking new challenges and opportunities for growth in a different environment.
• Looking for new challenges and opportunities to learn and grow

• Interested in working with new technologies or industries

• Seeking a better work-life balance or company culture

• Want to expand my skill set and experience
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Q1. GCD of 2 strings
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GCD of 2 strings is not a common concept in software engineering.
• GCD of 2 strings is not a standard problem in software engineering.

• It is more common to find GCD of integers or numbers.

• If the strings represent numbers, you can convert them to integers and find the GCD.
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Q1. Find edge score of the nodes in a directed graph
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Edge score of nodes in a directed graph
• Edge score is a measure of the importance of a node in a graph

• It is calculated by counting the number of edges that point to or from a node

• Nodes with higher edge scores are considered more important

• Edge score can be calculated using algorithms like PageRank or HITS
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Q1. Rotten oranges after every second in 2D matrix
Ans. 
Simulate rotting of oranges in a 2D matrix every second.
• Create a queue to store the coordinates of fresh oranges

• Iterate through the matrix and add the coordinates of fresh oranges to the queue

• Simulate the rotting process by iterating through the queue and rotting adjacent fresh oranges

• Keep track of the time taken for all oranges to rot

• Return -1 if there are any fresh oranges left after the simulation
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Q2. Java and Spring concepts, HTTP, HTTPS, OSI layers
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Q3. DB design for air ticket booking system
Ans. 
DB design for air ticket booking system
• Create tables for flights, passengers, bookings, and payments

• Use foreign keys to establish relationships between tables

• Include fields for flight details, passenger information, and payment details

• Consider implementing a caching mechanism for frequently accessed data
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Q1. Explain Concurrency
Ans. 
Concurrency is the ability of a system to execute multiple tasks simultaneously.
• Concurrency allows multiple tasks to run concurrently, improving performance and efficiency.

• Concurrency can be achieved through multithreading or multiprocessing.

• Example: A web server handling multiple requests simultaneously using multithreading.
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Q2. Explain Acid principles
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ACID principles are a set of properties that guarantee database transactions are processed reliably.
• Atomicity: Transactions are all or nothing. If one part of the transaction fails, the entire transaction is rolled back.

• Consistency: Transactions bring the database from one valid state to another. All constraints are satisfied.

• Isolation: Transactions are isolated from each other until they are completed.

• Durability: Once...read more
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Implement thread safe load balancer.
focus on input validations and cover all corner cases in tests