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Here’s your Interview Problem, Yesterday’s Solution and Tech Snippets for the day!

Industry News

Google, AWS, Microsoft, Mozilla and Huawei join together to create the Rust Foundation

Rust is a programming language that has gained a ton of popularity.

It’s been voted the most loved programming language every year since 2016 on the Stack Overflow Developer Survey.

It started as a side project inside of Mozilla in 2006 by Graydon Hoare. The language is intended for highly concurrent and highly safe systems.

Rust is compiled (machine code not bytecode), has strong static typing, imperative ( has some functional aspects) and has no garbage collection.

The benefits of Rust are

• Fast

  • The performance of idiomatic Rust is comparable to the performance of idiomatic C++

• Safety

  • Pointers in Rust are checked at compile time.

    • The compiler makes sure that every value has only one owner which means no double frees.

    • The compiler also makes sure that no pointers outlive the owner, which means no dangling pointers.

  • Thread Safety

    • Safe Rust guarantees an absence of data races. However, it does not prevent general race conditions. Read More.

  • No Hidden States

    • No Null Pointers in Rust. All references are guaranteed to not be Null.

    • Therefore, the compiler forces you to put in Null checks and helps you avoid runtime errors.

• Low Level Control

  • No Garbage Collector or Runtime

    • No garbage collection pauses or memory overhead

    • Can run on systems without an OS since there’s no runtime. Useful for embedded devices!

  • Control allocation and dispatch

    • Variables are all on the stack, but you can opt-in to heap allocation

    • Can opt-in to dynamic dispatch.

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Reddit’s valuation doubles to $6 billion dollars after a new $250 million dollar fundraising round

Reddit has more than 50 million daily active users and a nearly 90% increase in advertising revenue over the past year.

The company was previously valued at $3 billion dollars after a funding round in February 2019.

The company was first founded in June of 2005 and was part of the first batch of YCombinator, along with Twitch and Loopt ( a company started by Sam Altman, now the founder and CEO of OpenAI).

Now, the company has raised $250 million dollars in a Series E fundraising round to make investments in video, advertising and expanding into international markets.

Reddit is also planning on doubling the number of employees this year, with a heavy emphasis on adding programmers.

Interview Question

You are given a linked list as input.

Reverse the nodes in the linked list in groupings of k, where k is an integer that will be provided.

k is a positive integer and will be less than or equal to the length of the linked list.

If the number of nodes is not a multiple of k, then left-out nodes, at the end, should remain as they are.

Example

Input - 1 -> 2 -> 3 -> 4 -> 5, k = 2

Output - 2 -> 1 -> 4 -> 3 -> 5

Input - 1 -> 2 -> 3 -> 4 -> 5, k = 3

Output - 3 -> 2 -> 1 -> 4 -> 5

Here’s the question in LeetCode

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Previous Solution

As a refresher, here’s the previous question

Given an integer, convert it to a Roman Numeral.

Example

Input: 3

Output: “III”

Input: 4

Output: “IV”

Input: 1994

Output: “MCMXCIV”

Here’s the question in LeetCode

Solution

This question can actually be solved by a pretty elegant solution.

We first put all the possible combinations of roman numeral symbols and their integer values in an ordered dictionary (dictionaries are ordered in Python 3.6+ by default).

We put them in order from largest to smallest.

Then, we iterate through our dictionary and for each integer value, we divide the number by that integer value.

That tells us how many of those roman numerals we will need.

For example, 4000 will be represented as MMMM.

4000 / 1000 = 4, which means 4 Ms.

Then, we can add that number of roman numeral symbols to our character array (that represents the final roman numeral).

After, we can set our number to the remainder that’s left.

Then, we continue on to the next roman numeral, integer value pair in our dictionary.

Here’s the Python 3 code.

Can you analyze the time/space complexity of our solution?

Reply back with your estimate!

We’ll tell you if you’re correct (or we’ll tell you the answer if you’re wrong).

Best,

Arpan