Because there aren't many people, who are willing to spend extra hours to think of and make the best possible solution for just another codewars kata.

I was about to comment about this not handling ranges in descending order as well until I realised that the description specifies the numbers will be in ascending order.

Alas, I spent a lot of time making my solution work both ways :)

Pays to read the spec carefully. Good lesson.

thanks i

WHy don't you search by yourself? https://www.google.com/search?client=firefox-b-e&q=C%2B%2B+using

new to C++, what does the "Using" keyword mean?

sstream "<<" operator consumes a lot of memory so your solution probably has not less memory consumption

Good one, but I think it may be done with less memory consumption and faster (with one loop).
Maybe someone likes my solution: https://www.codewars.com/kata/reviews/5b6f4f7dc3a3f3fa54000862/groups/60295ceb27e2e40001f68a45

yes... exactly

While I did not do this kata using recursion, it's the perfect scenario for one! Anytime you're repeatedly performing a mathematical operation, where time is a factor, use recursion.

Calculating large determinants by Laplace's formula isn't smart either, yet it is fine enough to solve this kata.
There are other kata that require runtime efficiency and consequently have a higher kyu.

solutions without recursion are better

Wrong solution, author mentioned to not use sqrt

Copying of huge matrices isn't smart. Why many solutions have it?