Insert a string into another string efficiently

Question

I have

char aa[] = { \"Hello, !\" };

char bb[] = { \"World\" };

How to insert bb into aa the most efficiently with cstring

Answer 1

std::string aa = "Hello, !";
std::string bb = "World";
aa.insert(7, bb);

dont wanna use string from C++

Then why are you tagging this as C++?