Microsoft [Offer] Amazon [Offer] Two Sigma [Reject] Bloomberg [Reject] | Internship | U.S. | Summer 2020
I am a junior undergraduate computer science student at school that is ranked 60th for computer science in the United States. I applied to all companies on the Pitt CSC Github internship repo. I got many more phone interviews, but i'll just go through the companies that carried out the entire process for me (OA, phone interview, final round, etc.). I did not get online assessments from FAANG and unicorns. I only got through to phone interviews and final rounds for companies that send the OA to everyone because my resume gets screened out.

Microsoft Firmware Intern [Offer]
Online Assessment 120 minutes:

• Next greater element III on leetcode O(log(n))
• Given a set of positive integers, find the maximum possible sum of a subset such that the subset has a non-zero bitwise AND O(32 * n)
• We are given a compression algorithm that takes in strings that consist only of capital letters ('ABC...Z') and outputs a new string that would compress consecutive equivalent letters into the number of them concatenated with the letter itself (omit the number if it is 1). Suppose that we can remove any one K length segment from this input string. What is the minimum length that the compression algorithm can produce after the removal O(n)

This was definitely the hardest part of the interview process. I am pretty sure that I solved all of them with 100% accuracy, although we are not given access to all of the test case scores.

Phone Screen 30 minutes:

• Reverse words in a mutable string O(n) time, O(1) extra space
• General behavioral questions, questions about my resume.

This part was common for both SWE and FW interviews.

Final Round 4 hours:

• Implement int sqrt(int)
• N-queens from leetcode (Did not expect me to produce 100% correct solution)
• 2 more LC easy questions
• OpSys, C++ related questions

Had some small bugs but I quickly found the problems after adding print statements to analyze the programs.

Amazon SDE Intern [Offer]
There are so many online resources for this interview. Doesn't make sense for me to share my independent experience. I got this offer very early, before all of the OA solutions were posted online. Had a simple tree traversal and a simple stack question for my final round.

Two Sigma SWE Intern [Reject]
Online Assessment:

• Count squares in m by n rectangle with integer coordinate vertices, and any angular rotation O(min(m,n)).
• String question that could be optimized with a suffix array. I submitted an O(n^2logn) solution without a suffix array and failed 2 test cases to TLE

Phone Screen 30 minutes:

• Question related to picking out of a hat
• Gave me time to ask questions
  Solved this after thinking for 5 minutes. Needed to be a bit clever.

Final Round 6 hours total in 2 days:

• Similar to largest substring with maximum character frequency less than k
• Implement huffman encoding and decoding
• Suppose we have a food chain that can be abstracted to a directed acyclic graph. We want to group animals such there are no two animals within each group in which one animal is considered a predator of the other animal. Suppose M is the maximum group size among all groups. Find the maximum possible value for M among all possible ways to group the animals.
• Calculate approximate number of numbers in the first million rows of pascal's triangle that are not divisible by 7. (Math question, not coding)

I was caught off guard by the math question and I couldn't come to a satisfactory answer for it. I was able to solve all of the coding questions. I think what caused me to be rejected was my weak resume and low ranking school. I did not have all of the skills on the job posting.

Bloomberg SWE Intern [Reject]
Didn't have OA as I was contacted by a recruiter.

Phone screen 1 hr

• Oscillation sort of a string
• Flatten linked list with child pointers (Did not ask for the O(1) space solution)
• Word break ii

I came up with solutions for these pretty quickly. I used a trie for word break ii, which my interviewer wasn't thinking of initially.

2nd Phone screen 1 hr

• Design problem: implement k largest elements with a heap if you could take advantage of p computers that can do the computation simultaneously.
  • To solve this, interviewer wanted me to find the k largest elements for p equivalent partitions of the array simultaneously, and then keep deleting all of the minimums from each priority queue until there are k elements left in all of the p priority queues combined.
• Design problem: merge multiple incoming streams with a priority queue

I needed a hint for the first Design problem. It was probably the weakest part of my interview. I did the final behavioral round that felt like it went well, and then I was sent a generic rejection letter the next morning.

Conclusion
Pretty satisfied with the result. The salary for my offers is the same as what is reported on levels.fyi/internships. Wasn't expecting the Bloomberg rejection. Wish I could have gotten to interview for other FAANGs and unicorns.