Answer 1

Manav Roy

use insert function to do it 👇👇👇👇

https://code.sololearn.com/cvOZvU2lp2JM/?ref=app

Answer 2

Maybe split into char array or vector, then join to string with the separator?

https://www.programmingnotes.org/7679/cpp-how-to-join-concatenate-an-array-vector-container-into-a-delimited-string-using-cpp/