Your code does not comply to below

Note: if multiple products have the same revenue, order them according to their original positions in the input list.

Because you try to assig int to BigInteger. i variable is int, and Math.Pow(2, i) also returns int.

It depends on the programmer itself. Since the difference of such code neither impacts performance, speed nor efficiency (throughput) (in the current context), it is like asking should I start off with Javascript or Python as my first programming language? ^^

Yes. You want to make sure the password is 4-19 characters long only.

or cast to BigInteger. (BigInteger) Math.Pow() is the same as BigInteger.Pow()

https://learn.microsoft.com/en-us/dotnet/api/system.numerics.biginteger.pow?view=net-7.0

Use BigInteger.Pow instead.

Isntead of result[i] = (BigInteger)Math.Pow(2,i);, I wrote result[i] = Math.Pow(2,i); and it threw an error. Why?

I was wondering about this myself, thanks

How key=catalog.get works? I don't understand the .get.

What is % for? I read this explanation but I can't understand: https://www.php.net/manual/en/function.sprintf.php

% A literal percent character. No argument is required.

Thank you :)

Thank you :)

I like Number() better, it's clearer and easier to read