BillDesk Senior Software Engineer Interview Questions and Answers

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.
Answered by AI
Add your answer
Q2. Longest Palindromic substring
Ans. 
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
Answered by AI
Add your answer

Q1. Sort the elements of an unsorted array
Ans. 
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
Answered by AI
Add your answer
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.
Answered by AI
Add your answer

DP questions 1D DP and Array question

Q1. Java questions and technical questions from previous experience
Add your answer

Q1. Behavioural questions and standard HR questions
Add your answer
Q2. Why looking for job switch
Ans. 
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
Answered by AI
Add your answer

Q1. GCD of 2 strings
Ans. 
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.
Answered by AI
Add your answer

Easy Medium questions

Q1. Asked to design Basic Facebook.
Add your answer

Implement thread safe load balancer.
focus on input validations and cover all corner cases in tests

Q1. Low Level Design: How to do rate limiting for a platform serving 100K requests per second.
Ans. 
Implement rate limiting for a platform serving 100K requests per second.
• Use a token bucket algorithm to limit the rate of incoming requests.

• Set a maximum number of tokens in the bucket to control the rate.

• Refill the bucket at a constant rate to allow bursts of requests.

• Track the timestamp of the last request to enforce the rate limit.

• Consider using a distributed rate limiting system for scalability.

• Monitor and adjust t...read more
Answered by AI
Add your answer

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.
Answered by AI
Add your answer
Q2. Explain Acid principles
Ans. 
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
Answered by AI
Add your answer