OLA Interview Experience | Set 7 (For SDE-1)

I was recently interviewed by OLA, I could not make it after the last round. All rounds I had were telephonic, in the last round I was asked to code on collabedit.

Round 1 (around 35 min):
1. Given a matrix containing 0’s and 1’s. Find all the rows which are having 1’s at same position. Give all sets satisfying this.
2. In a stock market given are price of shares spread over a week. On what day should I buy and what day should i sell to get maximum profit.

3. Being a computer engineer why did I not opt for system side programming than web domain. (I had expr in web domain)
4. I had expr in web domain so he asked: What is the difference between web browser request and ajax call request.
— It is simple, by ajax call partial web page can be loaded.
5. Have you worked on ruby on rails?

Round 2 :
1. Given a matrix containing numbers. Find the 0’s and make all the rows and columns corresponding to that index as 0.
2. Design a structure for a File Uploader service (eg. Dropbox, google drive). It is a service where multiple people can upload
data at the same time and it also lists the top five uploaders (who uploaded the maximum number of files).
3. Puzzle: There is an employer and a worker, the employer has a gold bar of 7 units and he has to give 1unit each on a day for 7 days.
The employer has a magical knife which doesn’t work once it performs two cuts(1 cut divides the bar into two parts) on the bar.
How will you cut so that 1 unit on each day can be given to the worker.
4. Print left view of binary tree.

Round 3 :
1. He discussed what things they work on Ola. How these things are implemented. Like he mentioned of bar code a product has and catalog kind of thing.
2. I had to explain what project I am working on currently, what is the team size.
3. a)Since I had worked on SQL and databases, so he asked me what data structure will I use to implement a database.
–I gave hashmap as a soln (the key is our primary key and other fields we can store in an object which will be value for hashmap)
b)Now, If in case you want to find all names starting with a particular word (eg. ram….).How will you do that?
— gave trie structure as soln.
c)Now you need to find students whose marks are between a range i.e. between two numbers. How will you do, what data structure will you take in this case?
— a simple solution was that, take binary search tree and do inorder traversal of that (I couldn’t answer this, not clicked me)
4. Do you want to ask anything?

Round 4 :
1. The server receives a ping every 30 secs. The ping is load avg on the machine at that time. Find 90% percentile of the load average on the machine
at any time instant.
2. Find missing number in an AP.

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