Currently working at a tier-2 company.
Current experience : 3.5 years

I was contacted by the recruiter in the mid of september regarding an opportunity with Cohesity. They wanted me to do almost exactly what I am doing in my current company except they wanted it to be native. Honestly, I am not planning on switching anytime soon but I didn't want to lose an opportunity if it comes my way. Yes, we exist.

The enticing part of the offer was not that they gave me higher package or better amenities. I know the game too well to know what's fire and what's frying pan. It was that they offered me control over design and execution. Something I truly lack in my current company. There is no scope for original ideas in my current company and it's eating away my soul.

Back to what you're here for, The interview experience. I was adamant that I need a month of prep for any interview. They didn't listen. I started my prep on 2nd of October once I knew that not one but 5 companies are reaching out and that the market is in flux. I politely asked them to schedule the interview in november but they didnt budge. They asked me for interview slots which they didn't honor. It was not unreasonable. I am to answer my current company any given day. Still, I made way for the interview, thanks to nice colleagues. Cohesity's reason was that people do take interviews in lunch breaks as well. May be, but I am not the kind to talk with food in my mouth. (Relax, just a joke.)

Anyway, after 2 weeks of prep of which I researched Cohesity on geeks, leetcode and blind, I came to know that these guys are serious about OS fundamentals. I revised everything that I could (all the while managing my company expectations). DSA and Algo were ok for me. I can't do LC hards but I can manage LC mediums all day.

The day of interview, I called up the recruiter to know if this was coding/design/project demo round. You see, with the way recruiter spoke, I had prepped for all the three and I was weak in my knees if I couldn't present stuff properly. This, my dear friends is a RED signal. It is obvious to me now and most of you already. NEVER SHOW THEM YOUR INHIBITIONS OR WEAKNESSES.

The interview began thusly. He is the director in that company. Off the very start, he sounded judgemental to the core scanning every bit of my resume for solid 20 mins in 1 hour interview. All these 20 mins, it felt less like he was getting to know me and more of why I switched companies every 6 months. The second RED signal that the interview was doomed. I had this feeling that he might've already gotten the candidate he was looking for but I maybe dead wrong in this case.

He asked me a very very open ended question.

1. A large file of 1TB where every 4 bytes is a number, unsorted.
2. 10 TB of free HDD space. Use it however you like.
3. 100 MB of RAM. Very unrealistic if you know your comp arch, but let's humor him.

Find the missing ranges.

Example : 2,5,4,3,16,13,11,9,20
Answer: [0,1],[6,8],[10],[12],[14,15],[17,19]

I suggested brute force approch, straw man and tin man arguments.

1. Brute force : External Merge sort, compress the duplicates, iterate to get the missing range. He told me given file is immutable.
2. Straw man : Bucket the numbers as duplicates don't count, store it in a file in 10 TB free space, iterate through the files.
3. Tin man : Bucket the numbers as before but instead of storing values, use interval tuples instead, iterate through the files.

Finally, he asked me if there is any other data structure I could use. I thought of everything : stack, queue, linkedlist, array, Tree, BST, Trie, HashMap, Set, PQ and found that none of them fit the requirement. Bucketing with interval merge was my best shot.

Remember how I told you that Cohesity is very particular about OS fundamentals? Yep, the director told me that I could use Bitmap. My dumb brain didn't make the connection. He gave me couple of mins to think about it but nope. I missed it, mostly because it's about to end in 10 mins and I have to join scrum call. I threw in the towel.

He explained that we could assign each number to a bit in a bitmap and basically it's bucketing the values (0 not present, 1 is present). Now the question becomes, find the range of zeros in the bit-array. Funny thing about that, it's the LC easy question once you put it that way. The solution is O(log N).

I was close though. SO CLOSE!
I thought that at least they'll consider me for the next round but since I implied to the stupid HR that I'm not that prepared or because the director was griller, I was sent the rejection letter in under 4 hours.

Moral of the story : I don't know, be confident? Learn more about stuff? Keep yourself up to date?

Any ex-Cohesity people? What's the work environment like?