I try to make Burrows Wheeler Transformations

Question

https://code.sololearn.com/crMsU70AACp8/?ref=app
My code works fine for one condition but not if the input is empty. So, my function is <pair> returning function with string and integer returning parameters. It is said if the input is empty then you have to ignore integer parameter. But here is a problem because I do not know how to do that.
Thank you for your help.

Answer 1

how about

std::pair<std::string, int> encode(const std:: string &s = {}) {
// function body
}