☕ Big Tech reveals financials
Hey Guys,
Hope you’re having an awesome day!
We’re going to be trying something new out today. We’re running a weekly raffle for a Mock Coding Interview / Mentoring Session with a Senior Software Engineer at Google!
Details on how to enter the raffle are in the Interview Problem section below….
Interview Problem
You are given the root to a binary search tree.
Find the second largest node in the tree and return it.
Reply back to this email with how you’d solve this question. We’ll give you anywhere from 1 to 3 points depending on the quality of your answer.
You will always get at least 1 point for replying. So you should definitely give it a shot!
Every point you get is an entry into our weekly raffle!
This week’s raffle is a Mock Coding Interview / Mentoring Session with a Senior Software Engineer at Google!
As always, we’ll send you a complete solution with test cases tomorrow!
Industry News
Big Tech companies released earnings reports….
Apple
Earnings for the quarter slightly exceeded Wall Street expectations.
Revenue: $64.7 billion - up 1% year-over-year
iPhone revenue: $26.44 billion - down 20.7% year-over-year
Services revenue: $14.55 billion - up 16.3% year-over-year
Other Products revenue: $7.88 billion - up 20.9% year-over-year
Mac revenue: $9.0 billion - up 28% year-over-year
iPad revenue: $6.8 billion - up 46% year-over-year
Gross margin: 38.2%
Facebook
Earnings for the quarter greatly exceeded Wall Street expectations.
Earnings: $2.71 cents per share, vs $1.91 per share forecast by Refinitiv
Revenue: $21.47 billion, vs $19.8 billion forecast by Refinitiv
Daily active users (DAUs): 1.82 billion vs. 1.79 billion forecast by FactSet
Monthly active users (MAUs): 2.74 billion vs.2.7 billion forecast by FactSet
Average revenue per user (ARPU): $7.89 vs. $7.32 forecast by FactSet
In the US and Canada, Facebook’s user base fell to 196 million daily active users from 198 million a quarter earlier. That’s mainly because the user base had been elevated during the second quarter due to the impact of COVID-19.
Amazon
Earnings for the quarter greatly exceeded Wall Street Expectations
Earnings: $12.37 vs $7.41 per share expected, according to analysts surveyed by Refinitiv
Revenue: $96.15 billion vs $92.7 billion expected, according to analysts surveyed by Refinitiv
Sales: $112 - $121 billion dollars, up 28 - 38% year over year
AWS Revenue: $11.6 billion dollars, up 29% year over year
Google
Earnings for the quarter greatly exceeded Wall Street expectations.
Profit: $11.2 billion dollars
Digital Advertising Revenue: $37.1 billion dollars
YouTube Revenue: $5 billion dollars, up 32% year over year
Google Cloud Revenue: $3 billion dollars, up 44% year over year
Previous Solution
As a refresher, here’s the previous question
You are given a list of words as input.
Find all pairs of unique indices such that the concatenation of the two words is a palindrome.
Input - ["bat","dcba","lls","s","sssll", "cat", "tab"]
Output - [[0,6],[3,2],[2,4],[6,0]]
Solution
The brute force solution would be to check every possible word pair and see if they form a palindrome. There are O(n^2) word pairs and checking if a word is a palindrome takes O(w) time. Therefore, the time complexity would be O(n^2 * w)
Instead, we can create a hash table with all the words and then check all the prefixes and postfixes of every word. If the reverse of a word’s prefix is in the dictionary and it is palindromic, then we can add the indices of the two words to our dictionary. The same goes for a word’s postfix and the reverse of it’s postfix. The only difference is in that scenario, we have to reverse the order of the indices when we add them to our results.
This changes our time complexity to O(n * w^2). This will likely be a good tradeoff since the number of words will far outweigh the length of the words in most inputs.
You can view the Python 3 code with Test Cases here.
Don’t forget to reply to this email with your solution for today’s interview problem if you want to be included in the raffle!
Best,
Arpan