Hi Everyone!

Hope you’re all having a fantastic day!

Tech Dive

Our next tech dive will be on the basics of Distributed Systems!

With microservices being all the rage, distributed computing is more important now than ever!

We’ll be talking about the challenges that come about when you’re working with a distributed system and the potential solutions.

It’ll come out on Monday!

Our last tech dive was on Database Sharding!

• Database Sharding Tech Dive

Snippets

• Bitcoin reaches a new all-time high! The price of Bitcoin has now topped $23,000 dollars. Cue music. The Winklevoss twins wrote a pretty interesting article on Bitcoin a couple of months ago (back when it was ~$11,000) making the case for $500k a bitcoin. The main thesis is that inflation will increase in the coming years and that bitcoin is the best asset class to protect against it (compared to gold or other traditional inflation hedges).

• Google unveils MuRIL, a BERT model pre-trained on 17 Indian languages. The model is trained on corpora from Wikipedia and Common Crawl for 17 Indian languages.

• CoachHub raises $30 million dollars in their Series B. They develop a product that uses an AI-based matching system (hmmm) to recommend coaches for an individual where coaches teach skills like leadership or stress management. They’ve gone the B2B route with this product (whereas most similar products go B2C) and it seems to have worked well for them.

Interview Question

The set [1, 2, 3, …, n] contains a total of n! permutations.

You can arrange these permutations in order from smallest to largest.

For n = 3, the permutation sequence is

1. “123”

2. “132”

3. “213”

4. “231”

5. “312”

6. “321”

Given n and an integer k, return the kth permutation sequence.

For n = 3 and k = 2, the kth permutation sequence is “132”.

Find the most efficient solution ( better than O(n!) time-complexity ).

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Previous Solution

As a refresher, here’s the previous question

You are given a non-negative number n.

Count the number of primes less than n and return the count.

Here’s the question in LeetCode.

Solution

There are quite a few Prime Number Sieves conceived to quickly find prime numbers.

One of the most efficient is the Sieve of Eratosthenes.

Here’s a fantastic explanation of how the sieve works.

We implement the sieve using an array of booleans.

We set all the booleans to True as we start by assuming every number is prime.

Then, we use a for loop to iterate through all the values from 2 to sqrt(n).

For every prime number we encounter ( the value in the array has not been set to False), we iterate through all the multiples of that prime number. We mark each multiple as False (marking it as a composite number).

At the end, we can get the count by counting the number of True booleans. This can be done with the sum function.

Here’s a Python 3 REPL with the code.