help to optimize code

Question

Hello All,
Below is my code:
https://code.sololearn.com/c3O64jI4S5Tm
input and output is explained in code.
Request your view on the same in terms of optimization.
Thanks a lot for your input in advance...!

Answer 1

I recommend dropping std::regex and never to use it again in C++.
The standard library's regex is notorious for being slow.
There are some good 3rd party libraries out there, I heard of some really good template based regex library that works at compile time with c++20 if you can use that ( I forgot the name ) which I kinda doubt here.
So, unless you like to drink several cups of coffee while the program is compiling/running, I recommend just reading the numbers directly.

Answer 2

Okay